100cc Big Bore Kit ?

[Adam-NLV]

This is the first time I've seen these 100cc kits for the ct70. The auction page doesn't offer a lot of info. Is comes w/a Cyl Head. Does this look like a cheapO china kit? $144.00 It looks alright to me but my experience at engine building is very limited.

What do you pro-builders think?

2FASTMOTO Honda 100cc Big Bore Kit C70 CT70 ATC70 CRF70F Trail 70 ATC Ct | eBay

 

[power6994]

give it a miss.. how can it fit both z50 (6v) all the way through to crf50 (12v)

they are different..

 

[Enginedoctor]

it says the bore is 50mm. that's not 100 cc. 52mm on a 47mm stroke is 88…..

math must be different in china.

the guy is ibuyisell on ebay. i've bought things from him before, but it wasn't anything mini related. i think he'll just sell whatever.

 

[Adam-NLV]

it says the bore is 50mm. that's not 100 cc. 52mm on a 47mm stroke is 88…..

math must be different in china.

the guy is ibuyisell on ebay. i've bought things from him before, but it wasn't anything mini related. i think he'll just sell whatever.

Thanks EngDoc, yeah that is weird. The other thing is this kit includes the cyl and the head for only 44 bucks more than Dratv 88 kit, so how good could the head really be. Seems to good to be true.

I think they want $190 for a race head on other sites.

 

[Enginedoctor]

head (this is arguable) in terms of making Power, is the most important piece of the puzzle. sure, pistons, cranks and carbs are important (exhaust too), but the head really makes the engine 'flow' the way you want. i'd have no issue 'splurging' on a good head if i needed the engine to make power in a specific band.

i've heard a well ported/tuned stock head flows alright on the 70 platform, but if you really wanna make power up top you need a slight increase in compression over stock, to make up for camshaft overlap and things of that nature, and a head capable of supporting the flow from an aggressive camshaft. then you really start moving air (and fuel with it). the V2 is supposed to be pretty good. i haven't played any head games with the older platform stuff yet, but i'd like to. i have the old DRatv race head on my machine, with a 'middle of the road' camshaft. it's fairly aggressive, but not ridiculous. i like riding the bike on and off road so i'm not full throttle all the time.

 

[OLD CT]

That kit is BULL-SH*T,how can it fit from 69 up to a 94? It has a flat top piston....I say it fits 91-94... How long will it last before the head sucks a valve seat? Not long AT ALL....144 dollar head and cylinder? How can THAT be QUALITY???Lollololololol HAHA!!
Anyone that buys this is in for a big surprise..

Buy the 200 dollar TB race head Adam.

 

[cjpayne]

How long will it last before the head sucks a valve seat?

....Anyone that buys this is in for a big surprise..

X2 here OC. That's the gut feelin' I got when I read about it.lol. Too cheap to be true.

 

[Adam-NLV]

Buy the 200 dollar TB race head Adam.

Do you have a link to a race head that will fit?
This one? Trail bike Race Head ONLY Fits CRF50 - TBW0949 - Cylinder Heads & Parts - Pit Bike Engine Parts - TBolt USA, LLC

this is the only one I could find on the TB site. I think their other heads are for a 81 - 94 ct70, my application is 1973 k3.

 

[Adam-NLV]

OK, I think I figured out what your talking about: Race Cam TBW0189 http://tboltusa.com/store/advanced_search_result.php?keywords=TBW0189&x=7&y=7

And Race Head TBW0949: http://tboltusa.com/store/trail-bike-race-head-only-br-fits-crf50-p-1375.html

Both of these are $199

 

[OLD CT]

Yes Adam when I purchased my TB head I had to email Kenny at highprofilecycles and buy the head and cam sprocket separate.
TBW0939 is the kit #. The stock cam sprocket will not work,with this head. The carb in the kit is one of those shengways,not a good choice. Or I would say get the kit. Ebay item# 291256240610

 

[Adam-NLV]

Shouldn't I just get their 88 kit for $360? Vintage Honda 88cc Race Head big bore Kit CT70 K0 - 81 - tbw0939-CT70K0-81 - CT70 - TB Parts - TBolt USA, LLC

The doc's 88 kit is ~$100
TB Cam & head is ~$200

For $60 more there's a carb, cable and other stuff.

Is the Doc's 88 kit that much better?

Thanks OC

 

[Adam-NLV]

Thanks OC, I just read your post. I will get the eBay kit, saves me the hassle of shopping around diff sites & ship costs.

 

[OLD CT]

Just don't use the carb. You will have to buy a free flow exhaust or something like the trailbuddy thumper exhaust,I never tried one. Just basically saying you need a free flow exhaust. If you don't mind a little noise to wake up the white hairs on the road a NHRC pipe with some header wrap so you don't ''get burned'',would be a good choice. I will try to give you a budget carb recommendation to try on this build,unless you want a real mikuni...

 

[Adam-NLV]

Done got it. This bike should be a nice runner, I got it at 8 bills, don't mind putting a lil more in it to make it dang cool.

So a stock muffler with out the baffle won't get me to 50mph? What is the potential for a kit like this? All I want is to get out of the way of these drivers on 45mph speed limit roads.

On the carb, I'll research that subject some more...What about a stock re-jetted oem carb? Hate to run a twenty dollar special, rather have the quality one, don't mind spending but will have to wait till next month for another payday. need a HV oil pump too.

 

[OLD CT]

The hi flow exhaust will get you moving into traffic quicker. I feel every little detail done right,will bring up the mph close to 55.
Head,bore kit,hi flow ex,aftermarket carb. You wont get the same punch with a stock carb/exhaust.