Trans mounted clutch... TRX90

SS LS1

New Member
Raising engagement speed will decrease clamping load and, with it, grip power......

Whether a lightened rotating assembly and higher initial engagement (a.k.a. stall) speed is a good thing depends on whether you're racing or road riding......

A fraction of a second quicker 0-20mph time will be all but irrelevant, in the "stoplight grand prix." Reduced longevity doesn't play well if you want to get some real miles out of the bike.

...... if your usage plans are for low mileage and short rides...well...maybe a peaky & tweaky race setup is the way to go, if that's what suits your tastes...

To be clear, mine is a skewed perspective...serious road use, i.e. long rides and over a number of years......

Thanks for your input and confirming what I was suspecting that lightening the rotating asembly would reduce clutch clamping load.... So what about increasing the clutch shoe retaining spring pressure (TRX 90 style clutch) to allow stall rpms to be raised before initial clutch engagement? By keeping the shoe weights origional the overall clamping force should remain the same then. Also don't see a way to increase stall speed on the all in one centrifugal clutch assemble without going to less cam actuators which most definitely would alter clamping force.

Much like yourself my perspective is skewed in the complete opposite direction.

Don't personally care about racing, street riding or 0 - 20 mph acceleration at the stoplights as I'm running ATC 70's which will never see street use or high milage obviously. I will keep manual clutch motors in my CT70s as I really don't see any advantage having a hp limited semi auto clutch on the street where it's hard to stall your engine in the first place.

I ride my ATC 70s in fields, hills, sand dunes and along ditch ways much like riding in a half pipe. Often come to an abrupt stop, need tight manuvering and a quick rev to get up short steep incline surfaces without stalling the engine which might cause a backflip problem. Hence the idea of a semi auto clutch and increase stall speed adjustments. (Unique skewed perspective)

I have a nasty ported, cammed and high compression 150cc in another ATC 70 that flies but it is difficult to perform the same manvers with its low mass transmission mounted manual clutch. It is hard to not stall the engine and it doesn't lug very good due to the minimal flywheel effect even with very low gearing for controlled hill climbing.

Either way it sounds like most have not ventured into changes of stall speeds in semi autos so it would be uncharted territory which I don't need to venture into. It also means my 2 in one crankshaft semi auto clutch is limited in options. However a TRX 90 split clutch setup might work nicely by adding a manual clutch lever modification and keep the centrifugal clutch intact. It would live a long semi auto life, eliminate engine stalling and if needed allow one to rev up the stall speed temporarily by slipping the manual clutch plates with a hand lever in tough situations.
 

kirrbby

Well-Known Member
eliminating/avoiding obviously risky stuff... unknown parts with no field service history...and you're well on your way to something that will at least stay together & running.

Beyond that, breakdown the engine build into lower & top ends. Power is made in the top end assembly. The lower end has to apply the power and survive it.

Thus far, you've got a Takegawa clutch conversion & crank, feeding into an OEM Honda tranny. IMHO, that's rock-solid quality stuffs.(n)

That said, I think you've got most of this pretty well planned-out. Going by what you've posted in this thread, so far, the biggest unknowns will be the clutch discs and which alternator to use with the AWOL centrifugal clutch. I can't see those things holding you back.

With the #2 engine...
The tb V2 head is still kinda risky. But I wanted to try it. I'm more in experimentation/learning mode than rock solid last forever mode. I'll gamble with the top end for sure, as it's fairly easy to repair/replace/change anytime I get the urge.

I didn't actually get the Takegawa clutch conversion. I just bought the cover, and the parts that I think I need to make it work with the STOCK Honda clutch. This is all about converting the motor to a manual clutch, plus kickstart, and...it's pretty. This has definitely been done before, and CHP sells the "kit" kinda. What I would like is the instructions...I do not think there ARE any instructions. This leaves plenty of room for missed parts and mistakes, and is my biggest concern. I'm reasonably confident that I know how to make it right, or that I can figure it out when I start putting it together.

The alternator is no sweat. I might try one, then another, and try to notice the difference. I'm just not sure if, or how easy, I could damage something if the balance between the weight of the flywheel and the missing clutch is too different.

I understand the semi-auto setup now, which should help a little during and after getting the first motor built. The second engine is still in the planning/research stage...it'll be a while before I build that one.
 

69ST

Well-Known Member
I ride my ATC 70s in fields, hills, sand dunes and along ditch ways much like riding in a half pipe. Often come to an abrupt stop, need tight manuvering and a quick rev to get up short steep incline surfaces without stalling the engine which might cause a backflip problem. Hence the idea of a semi auto clutch and increase stall speed adjustments. (Unique skewed perspective)
That is good to know, as it could make a huge difference, enough that, in terms of theory, what you suggested (that increase engagement & stall speed) sounds reasonable imho. Higher engagement speed also means higher disengagement speed. Unfortunately, that's about as far as I can really take the specific, technical, discussion; ATVs are outside of my direct experience. You obviously need some longterm durability and increased stall speed works against that, unless dealing with a fluid coupling (automotive torque converter), or specially engineered friction linings...that I've never heard of, for these motors. OTOH, if you're not doing a lot of standing starts, the lighter flyweight approach may be viable for you.
Adding a manual clutch function, OTOH, ought to be able to deliver the results you want since, at this late date, you must have more than enough technical riding skill.


With the #2 engine...
The tb V2 head is still kinda risky. But I wanted to try it. I'm more in experimentation/learning mode than rock solid last forever mode. I'll gamble with the top end for sure, as it's fairly easy to repair/replace/change anytime I get the urge.

I've gone kinda sour on aftermarket roller-rocker heads. It's not that they can't deliver the airflow but for how long, before something fails. The Takegawa +r head, that the V2 copies, had rocker failures early on. At that time, standard lore had it that s30 was the hairiest profile cam one could use without rapid failure. That was also before the "D" versions were released. Since then, I've been a little shocked and a lot disappointed, to learn of problems with both. Perhaps an s20 profile would be better, for mileage. At that level, however, you can get the same power from a non-rocker head, running an old-type r20, Z40, etc...and those conventional rockers are very reliable. There was at least one lot of V2 heads with incorrectly machined valve guides..uncharacteristic for tb products...that should be easily correctable, using a guide reamer.

Agreed, if something in the top end goes "bang!!", it'll be over quickly enough that the lower end survives and top ends can be swapped quickly.

IMHO there's nothing wrong with taking a chance on something new & novel. That falls under the "trial & error testing" category I frequently mention here. It's the road to improvement...and paved with broken parts. Think of that shop scene in the flick "World's Fastest Indian"...the shelves of broken parts labeled "offerings to the god of speed". The process can be a lot of fun, and ultimately very satisfying once you've realized some successes. You seem to be going in with realistic expectations so, this ought to be interesting.
 

SS LS1

New Member
Kiirrby, As far as the V2 head goes it is a proven HP maker so I'm not sure what you mean by risky unless you are thinking a matching head and piston combo may not be available for your particular bore and stroke application.

This winter I plan on adding a V2 head to either my 114cc or on one of my 150cc engines, just can't decide which one I want to do first. I have been very impressed with the results of the last two heads I have ported and swapped larger cams (Z40, TB300) into that I am intrigued by the idea of swapping to a V2 head. The larger valves and the higher cam lobe ramp rates allowed by the roller rockers is a proven way to make HP.

My only concern is they sell the same V2 head with the same cam, valve diameters and port sizes for engine sizes from 88cc all the way up to 190cc (same for the big dollar Takegawa +R head). There is no way the head is optimized for all those engine sizes so it's likely best for something in the middle and way oversized for 88cc and undersized for the really big engines. Just not sure if the V2 head ports would be too big for a 114cc engine that it would kill all the bottom end power.

From my limited research the V2 head issues with the improper valve guide diameters was an isolated batch way back in 2012 that does not appear to be a reoccurring issue in the last 5 yrs. So I'm not too worried about an uncommon head defect to take the risk. Good to note that if there was any roller head part failures that the Takegawa +R parts will swap right in I'm told. But the TB Parts are so cheap and easily available I would likely just buy those instead.

Either way, great discussion and really appreciate opinions and personal experiences shared on the forums both with success and failures of parts.

Sorry for the thread hijack! ..........
 
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kirrbby

Well-Known Member
There is no thread hijack.

I say the tb v2 is risky, because I've seen such mixed reviews. OR...no reviews. BIG hype when it was introduced, then...crickets...for a loong time. Even now, I have a hard time finding one on tb's website...advertised for a ct70 etc. If they were great, I'd think they would plaster it up in big clear text...THEY'RE GREAT! They don't do that.
Fatcaaat posted in his thread about 3 rebuilds in 12K miles.

I think they run great. Question is, for how long?

I'd like to consider the Taky 2 valve, solid rocker, head...if only I could figure them out. +R, -r, V2+R, D series??? WTF is it. Can't seem to get the straight dope. I can't read code. I just wan't to know what it will work with, valve and port sizes, pros and cons would be good. I don't mind spending money on good parts, just not willing to gamble 6-$700 on a misread secret code. Does anyone want to demystify Takegawa heads for us?? I haven't looked into the Kitaco heads yet. If they do a better job with American marketing, I might be in. Taky crank, clutch cover, cylinder, and a Kitaco head?? I'd rather keep with Takegawa, but not until I know what I'm buying.
End rant.

I wanted to try the tb v2 head, to see what I think, and see if it seems to hold up.
But the more I look into it, the more I think I just want to stick with the Honda TRX90 head.
 

69ST

Well-Known Member
Rollers, whether rockers, or lifters (automotive engines) allow for valve acceleration rates that would not otherwise be mechanically possible. That makes it possible to balance peak power with under-the-curve power, i.e. a lot of usable power, not just peaky & tweaky. That said, keep in mind the differing perspectives here. The heads you mentioned do support additional airflow and airflow equals power potential...horsepower is made in the head. OTOH, none of the available roller-rocker heads for these engines, has anywhere near OEM durability. The occasional rocker failure aside, valve/seat/guide wear is far more rapid than it is with OEM heads. For those of us with road bikes, that's an issue. For those of us with limited use machinery...including ATVs:whistle:...maybe not so much. It's worth mentioning, for the sake of allowing folks to make the most informed decision possible imho.

My only concern is they sell the same V2 head with the same cam, valve diameters and port sizes for engine sizes from 88cc all the way up to 190cc (same for the big dollar Takegawa +R head). There is no way the head is optimized for all those engine sizes so it's likely best for something in the middle and way oversized for 88cc and undersized for the really big engines. Just not sure if the V2 head ports would be too big for a 114cc engine that it would kill all the bottom end power.

This is a central issue. "Optimized" has to be defined. Power potential is determined by the head and it can only flow so much air. Airflow = horsepower. OTOH, there is only so much power that one of these little motors can deliver...and survive. From what I've seen, a +R head can support up to ~75-80mph, tops, without mods and that takes ~125-140cc displacement. Above that, additional displacement, especially stroke length increases, deliver mostly torque increase paired with smaller hp gains. At 88cc you might be looking at a pure screamer tune, ~60mph top speed potential and a powerband from ~6000 - 13000rpm. At the other end, 175cc, more like 80-85mph and the engine runs out of breath at 8000-9000rpm, tops...a pure stomper. As with anything else, there are tradeoffs; you have to decide where the best balance lies.
 

69ST

Well-Known Member
There is no thread hijack.

I say the tb v2 is risky, because I've seen such mixed reviews. OR...no reviews. BIG hype when it was introduced, then...crickets...for a loong time. Even now, I have a hard time finding one on tb's website...advertised for a ct70 etc. If they were great, I'd think they would plaster it up in big clear text...THEY'RE GREAT! They don't do that.
Fatcaaat posted in his thread about 3 rebuilds in 12K miles.

I think they run great. Question is, for how long?

I'd like to consider the Taky 2 valve, solid rocker, head...if only I could figure them out. +R, -r, V2+R, D series??? WTF is it. Can't seem to get the straight dope. I can't read code. I just wan't to know what it will work with, valve and port sizes, pros and cons would be good. I don't mind spending money on good parts, just not willing to gamble 6-$700 on a misread secret code. Does anyone want to demystify Takegawa heads for us?? I haven't looked into the Kitaco heads yet. If they do a better job with American marketing, I might be in. Taky crank, clutch cover, cylinder, and a Kitaco head?? I'd rather keep with Takegawa, but not until I know what I'm buying.
End rant.

I wanted to try the tb v2 head, to see what I think, and see if it seems to hold up.
But the more I look into it, the more I think I just want to stick with the Honda TRX90 head.

"D" = Decompression cam assembly. With the bigger displacement tunes, especially those with long 55mm+ stroke and high cranking compression, a decomp cam makes starting less traumatic on engine and rider.
"+R" is the current generation of the Taky superhead, it uses roller rockers. "V2" is the trailbikes copy of the +R head.

With cams, the old superhead used 12v Honda configuration and offered them in R10, R15 & R20 grinds, the bigger the number, the more aggressive (high-lift, lots of overlap) high-rpm/hp biased the profile. With the +R head, there are profiles available from s10 through s35; through s20, they're close to the earlier "R" versions. Presumably, R20 was the practical limit without roller rockers.

Personally, I'd steer clear of the Kitaco head. Not that Kitaco quality standards are lacking...they aren't. That said, I've known fewer than a half dozen guys who've run these, since the late `90s, only two live on this side of the pond. And, Kitaco chose the old 6v-style plain bearing cam (WTF?). From what I was told, they worked well. Too much of a mystery, too little feedback and less than no stateside support of any kind, imo. If you're hoping for better marketing of high-end Japanese parts, to the US market, don't hold your breath. There's not enough market demand. Here, price gets the top spot on the priority list. So they're not going to pursue US buyers...interested US buyers have to pursue them. At least now we have webike. Closest you'll get to US-friendly marketing is an EU vendor; European languages tend to translate better into English, than Japanese does.
 

kirrbby

Well-Known Member
Thank you very much for that info racerx.

I thought the Superhead was a 4 valve head... 4V+R is what I'm seeing. Everything I see that says +R is 4 valve.

So what do they call their 2 (big) valve head, that's NOT a roller rocker?

■ 17RStage+DCylinder head < this looks like the 2 valve head without roller rockers. webike says the head-only is discontinued. I can find it as a BB kit, with cyl and piston, but few details...63 or 69mm.?? and how big IS the piston?? lol. Some show the cc,s of the kit. I spose the 124cc kit is the one I'd need. 124cc...54x54 would require a 69mm tall cylinder. Seems like they could mention the sizes of stuff. geesh.

Haven't found a 2 valve WITH roller rockers yet.

https://japan.webike.net/products/21974358.html

https://japan.webike.net/products/22956070.html
 
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OLD CT

Well-Known Member
Just looking by looking at it, I will say it's NOT the 69mm cylinder.
So you would need to but a 69mm from dratv or whoever and use this one in the future. MO MONEY!:mad::cry:
 

fatcaaat

Well-Known Member
The V2 head I had put on this motor had issues with the guides in that they were too tight. That caused the valve to seize and the piston to crash into it. It wiped out the piston, cylinder. Once the guides were honed out to the right tolerance and new valves installed, it ran 5000 miles. At that point it needed new rockers and the valves were starting to tulip. Another 5000 miles and the valves were shot completely and replaced. The guides had some wear but were in tolerance. I think 2000 more miles there were other issues with the top end.

I think TB has modified the design quite a bit since the early ones. I think they now have improved the rockers themselves as well. Honestly, the TB cam that comes with it is a direct copy of the Takegawa s25 as is the rockers, valves, etc. The parts swap directly with the takegawa version of the head.

The biggest advantage of using the takegawa parts is that you can get a decomp cam which makes kicking it as easy as a stock 70. Trailbikes produces good stuff and has a great reputation. I don't think the V2 is a failure, you just have to realize that its service interval is simply shorter.

When I rebuilt the 142cc to put in my personal bike, I swapped out the V2 after it had been completely rebuilt, and put on a stock honda Nice head. Why? Because I wanted the engine/bike to be dead reliable without having to worry about anything and the shortest interval part was the head. I am definitely giving up power here..that's evident, having ridden this engine with the V head and stock head...but there is the question...can I live with less power to gain service life? On this particular bike, that's what I chose.

Takegawa still sells the 2v+r head as part of a kit on webike. The advantages of using Taky parts over the TB parts are superior valves, better rockers, and titanium retainers. It also looks better IMO.
 

69ST

Well-Known Member
The biggest advantage of using the takegawa parts is that you can get a decomp cam which makes kicking it as easy as a stock 70. Trailbikes produces good stuff and has a great reputation. I don't think the V2 is a failure, you just have to realize that its service interval is simply shorter.

Well put and I agree. I have virtually zero reservations when it comes to tb parts...the V2 head being the rare exception and for the reasons stated. Swapping-in Takegawa pieces might solve the rapid (IMO) wear issues. But then the cost savings would be marginal.

Aftermarket manufacturers fight an uphill battle. Honda is a major OEM with a seven-decade headstart; they invented this stuff...literally...and have huge resources to keep refining it. They also have a reputation to maintain. And, the real capper, economies of scale. IMHO, it's amazing that anyone in the aftermarket has gotten as far as we've seen. None of which changes the basic issue...longevity. That leaves one forced to choose between peak horsepower and OEM durability/longevity. FWIW, I don't criticize TB for not replicating Honda service life, that would increase costs, top-to-bottom. High-mileage riders are relatively few & far between. Would there be enough units sold to make it profitable? A business that sells at a loss won't last long.

If you're among the majority, for whom 5000 miles is almost unimaginable, service life may not matter. OTOH, if you're a long-termer, it'd be wise to plan ahead to avoid disappointment. BTW, that could also mean buying service parts well in advance. Replacing an intake valve every ~5K miles wouldn't necessarily be the end of the world, if you're otherwise all grins over the setup...and you accept that as part of the deal, going in.

OTOH, if you're among the growing roster of longterm, high-mileage, riders, the OEM 12v heads are amazingly durable. I'm talking 20,000+ miles and still healthy...verified. I've seen others, of unknown but clearly higher mileage and nary a tuliped valve, worn seat, or guide among them. But, as Jarred pointed out, they don't flow like a +R, or V2. That's the "apples-to-oranges" comparison you have to make before deciding which is the best choice. That's another weighty topic, for another time.
 

kirrbby

Well-Known Member
The tb V2 head has been around long enough that I'd be very comfortable buying it now. I'm sure they have the kinks worked out at this point.

My head is still spinning from looking thru Takegawa heads and kits. The 2nd link that fatcaaat posted does look like the one. 2 valve roller rocker setup for $700. I don't need the cylinder itself, but a spare would probably be good. It does not look like that one has the decomp cam, so it would be a good comparison to the $425 tb V2 kit minus the cylinder. A extra $275 for Taky quality, and a spare cylinder. Plus the fact that it definitely IS better lookin. (I don't care for the THREE covers on the tb part that say tb parts. I'm sure I can find replacements that look nicer.

I'm really leaning toward just getting the tb v2. That was my initial plan...to try it. Plus it's cheap and complete. 5000 miles is more than I've ever put on any engine, and I'm optimistic that it could go farther than that.
The Takegawa part seems like it would be something that I might end up with AFTER i'm done experimenting with everything else. In fact it seems that Honda Nice engines are where the educated guys end up.

I could certainly just take some good advice, from the people who know, and just build 3 or 4 lifetime engines and be done with it...

Naa...too easy. lol I'm not there yet.

https://tboltusa.com/store/tbparts-...kit-for-114cc-br-for-honda-trx-90-p-8610.html
 

kirrbby

Well-Known Member
The stuff in pic #1 came with the clutch cover.
#2 is the extras I ordered to make it work with my TRX motor. I know the primary gear I bought won't work for me. I learned that from fatcaaat's 1st post, a couple days AFTER I ordered it...I need a 17 tooth. Think I found one.
#3 shows the other side of the cover. The pusher that disengages the clutch. And the nipple that supplies oil to the crank.

IMG_20171126_171738662.jpg
IMG_20171126_171756120.jpg
1511735205509495349847.jpg
 

kirrbby

Well-Known Member
The motor that I've been using for example...for my pictures, is one that I started building a long time ago. I was going after it as a quickie, throw it together for a try, kinda project. I got a lot of advice and such from Terry, before he disappeared, and from fatcaaat too. Terry gave me a Kickshaft setup to use. The type he gave me, required me to drill and tap the bosses inside of the left engine case, since this type of shaft uses a couple screws to retain the shaft and spring. I was never really confident with my job on the drill and tap. So the quick easy TRX90 big bore project stalled, just after I had the clutch side assembled. So now, I have a different kick shaft ready to replace the one that's in it. The new one is held in place Honda style, so I won't need to use my poorly tapped holes. (actually, I think I bottomed out the screws, and may have damaged the threads)
I'll save the first kickshaft for another engine, where I'll have the experience now to do a better job installing it.

This engine will be the 114cc. It should be quick and easy since everything has already been gone thru and cleaned. I'm excited about the 114, because I love that it retains most of the original parts, working together as Honda designed them. Where else can you get a Honda based 114cc engine for only about $250-300 worth of big bore parts (on top of the core engine)
$100 kickshaft, $150 BB kit, 50 to machine the engine cover for the kicker. 54mm bore x 49.5 stroke. Oversquare...high(er) revving, engine that'll bolt up into a Z50/CT70.

Better pick up your own TRX90 core engines now boys...I'm about to drive up prices as I post a crapload about building the 2 I have planned.

I'm getting close to being ready to dig in to the first.

Everybody is gonna want one. lol
 

kirrbby

Well-Known Member
My money was on, I'm just gonna put the reliable stock Honda Nice head on and not have to worry about it.;)

That is a great back pocket option. Or the TRX90 head it seems. How about sending a TRX90 head to a Pro, for porting and...other magic upgrades.

Believe me, That is right up my alley...upgraded reliability, done right.

There has to be SOMETHING to these race heads tho. Otherwise they wouldn't be selling any of them at all.
 

OLD CT

Well-Known Member
When I think of the 4v race heads I personally think of a kid racing motocross looking for a edge on the competition not far from the race hauler, not touring or riding 50+ miles away from home with no roadside assistance! They would have no problem ripping the engine apart after a couple of races either.:)
 

fatcaaat

Well-Known Member
Well, I have a 127 4v+r Nice motor with about 2400 miles on it so far. Never an issue with it! I do think I"m wasting it a little though as I have not lightened up the rotating assembly...still rocking stock flywheel and oil slinger.
 

OLD CT

Well-Known Member
You rack up more mores than me for sure, I have 3 CT's that all have stock heads and one with a old TB 2 valve race head. That is the 124cc. It's good for 70+ or - a couple mph and that is fast enough for me. All in under $1000 bucks for the 124. As a matter of fact, that is the most $ I have into a engine... None have been apart yet. I will say riding around my neighborhood is way different than most as I can't seem to ride more than a few blocks without some asshole pulling out of a side street, right in front of me!
I usually take the bike 30 miles in the car to a safer riding area to rack up some miles.
 
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