18t is tight on a new-gen motor, such as a Nice 110. I'm not wild about the fitment. A 49cc-based motor will have less clearance...not good, imho. Mo`better to go with the 30t cog which you already have. That'll be roughly equivalent to adding 1 tooth at the countershaft. If that's not enough, you may be able to drop down to 29t; 28t would require some lathe work to the hub. Anything smaller and you'd need an aftermarket hub.
Clone to Honda conversion
- Thread starter Deoodles
- Start date
Roy Chambers
Member
Well, the first picture tells most of the information. I don't see any signs of the Dome hitting at all, but the Squish band look's close. But I don't think that it is hitting ether, cause the Piston appears to be down in the Bore some. What I do see that look's like it might be trouble is the Exhaust pocket radius not being machined far enough to the edge of the piston. Another wards, the radius is big enough, and it's deep enough, it's just not moved far enough to the edge.
This can easily be fixed with a 1/8 burr, just roll it back a Small amount, just to make sure it's not a problem later at high RPM.
The other thing that is very troubling to me is, LOOK at the Cylinder, it look's like it is moved over to the Right.
All 4 Studs seam to be rubbing the Cylinder on the Left side. Now i don't know anything about them big bore Cylinders, maybe that's just the way they fit. To me, it's like the through hole is not Concentric with the dowel pin holes.
Two things come to mind, one is you said that you had to ream out the Dowel pins in a earlier post. The other thing that i have seen a million times before on Car Engines, Is like an Rocker Arm assembly with the Cam caps made to them. They have then same Thin Dowel pins in all 5 Cam caps, so that's 10 Dowel pins, ALL Smashed and Squished over! The guy putting it tougher never even noticed it and just tighten it down.
Now that i have pointed this out, maybe someone else, that has installed a lot of them can comment.
Thanks Roy.
I’ll try. The dowel pins line up the cylinder to the block not the studs. I did have to ream 1 or 2 out. The inside so they would pass over the threads on the studs, not that uncommon I suspect.
You may be on to something with the piston I just don’t know. I did enough work on it and spent more than the piston on gaskets. A new piston makes sense to me at this point. I do agree with your assessment though.
You may be on to something with the piston I just don’t know. I did enough work on it and spent more than the piston on gaskets. A new piston makes sense to me at this point. I do agree with your assessment though.
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That does appear to have a lot of deck height to spare. However, this all boils down to static CR and with a dramatic stroke increase it may be exactly what is needed. Looks to me like the dome, itself, has zero deck height, at TDC. Guesstimating 4mm deck height, at the squish band, with a 54mm bore, there's ~5cc added to the combustion chamber volume, with the piston at TDC. Don't bet the farm on these guesses...engine building via photographic measurements is not much better than throwing darts while blindfolded. Reviewing your prior photos, it appears that the old piston had some positive deck height, at TDC, as well...making visual comparisons even more useless.
Four possibilities come to mind:
Four possibilities come to mind:
- Ask the vendor. He should be familiar with this head/piston combo.
- CC the head & piston, as-installed.
- Assemble the engine and break out the compression tester. Anything over 150psi, cranking compression and you should be fine. Much below that and it's time to look for a different piston; at least no parts get sacrificed in the process...other than a head gasket.
- Assemble the engine and hit the "seat-of-the-pants dyno".
kirrbby
Well-Known Member
Do you have a base gasket in there Deoodles...in the pic above?
Are the surfaces completely clean?
It seems like a lot to me too, but I'm no expert for sure. I do think a little less compression might be good...especially with your stated goal for this engine.
Too much compression will make you cringe each time you try to start it cold. Feels like the kicker setup is at max capacity. You like it to start, first careful kick.
But I'm not sure how much the performance will be affected if the compression falls a little low.
I vote, grab your pistachios and bolt it together.
It's only money, and time, and...
Are the surfaces completely clean?
It seems like a lot to me too, but I'm no expert for sure. I do think a little less compression might be good...especially with your stated goal for this engine.
Too much compression will make you cringe each time you try to start it cold. Feels like the kicker setup is at max capacity. You like it to start, first careful kick.
But I'm not sure how much the performance will be affected if the compression falls a little low.
I vote, grab your pistachios and bolt it together.
It's only money, and time, and...
Lol Kirrbby. I spent some time comparing the pistons tonight. They are definitely apples and oranges. My first attempt failed because the head is new style and the piston is old. The new piston is about 1.2 mm lower in the deck and the skirt is 3mm shorter. The new piston also fits inside the head and the other does not. The dome is 4mm shorter as well. It is the better choice. I can also ditch the aluminum 1.2mm gasket for a much thinner one. I’m going to go with it. I need a road bike not a race bike.
STOP! After sleeping on this I have decided I don’t want to build a 124 that ends up being a 117 with low compression. I need an old dome head with large valves preferably to complete the build properly. Beatrice is the only one I found. E22 I think. Anyone have any experience with this head or other source options? Are there any solutions I’m not thinking about?
Thanks
Thanks
At this stage of the game, you've already got everything needed to complete the assembly. May as well button it up and see what your compression gauge reads. I'm guessing that you had ~12.5:1 static CR with the last piston...maybe higher, judging by a.) the interference problem and b.) that the new piston is both recommended for the application and it's probably not as dramatically different as it appears in your pix. As long as you have at least 8.5:1 static CR, the thing should make low-to-midrange torque well enough, especially if paired with a mild cam...that'll really bring-up low rpm cylinder pressure. Can't imagine this thing not being able to pull 60-65mph, minimum, even with a mild cam profile and marginally acceptable (on the low side) compression.
Dunno about the longterm implications of the DRatv "E22" head. I've used a few of them, without incident. However, I also have no idea how many miles any of those have seen. On the "pro" side, I like ball bearing cams over plain bearings...way more durable and more profile choices.
OTOH, there's nothing inherently wrong with the old (6v) style CT70 head; it has the biggest ports & valves, other than the CF70 Chaly, which never saw North American shores. (The TB head is, essentially, the old CT70 head but machined for 12v/ball bearing cams.) Not that big of a deal to rebuild a classic Honda head and you'd never let the oil get dirty enough to erode the cam journals. The "con" side, limited cam choices...basically stock, SL70/"fast road" and "race".
I don't think that you can go too far wrong. As long as you're sticking with the same combustion chamber (dome) configuration, a head swap is quick & easy. That includes swapping-in another head, should you end up with less than 150psi cranking compression, or the real world performance turning out to be too soggy for your liking. Should the inexpensive "E22" head defy expectations and turn out to lack durability, a head swap would mean "no BFD". IMHO, the chances of a failure are small.
Dunno about the longterm implications of the DRatv "E22" head. I've used a few of them, without incident. However, I also have no idea how many miles any of those have seen. On the "pro" side, I like ball bearing cams over plain bearings...way more durable and more profile choices.
OTOH, there's nothing inherently wrong with the old (6v) style CT70 head; it has the biggest ports & valves, other than the CF70 Chaly, which never saw North American shores. (The TB head is, essentially, the old CT70 head but machined for 12v/ball bearing cams.) Not that big of a deal to rebuild a classic Honda head and you'd never let the oil get dirty enough to erode the cam journals. The "con" side, limited cam choices...basically stock, SL70/"fast road" and "race".
I don't think that you can go too far wrong. As long as you're sticking with the same combustion chamber (dome) configuration, a head swap is quick & easy. That includes swapping-in another head, should you end up with less than 150psi cranking compression, or the real world performance turning out to be too soggy for your liking. Should the inexpensive "E22" head defy expectations and turn out to lack durability, a head swap would mean "no BFD". IMHO, the chances of a failure are small.
kirrbby
Well-Known Member
I've been hunting up parts last couple days. I took a close look at a trx90 head. The combustion chamber is smaller than the CT70 big dome. But I think it's bigger than the 70 "new dome", but I didn't have one to compare. So I'm afraid to say that it will work without researching it a bit. I do think that dratv says the 90 head works with big dome pistons. And I'm running a "big dome" 54mm piston in a trx90 engine on my 93 right now...my "trans mounted clutch" thread engine.
I think it's this one...says for stock trx or tb v1 heads. So maybe it's not a big dome piston.
https://tboltusa.com/store/tbparts-789-piston-54mm-114cc-for-trx90-china-90-110cc-p-423.html
The best TRX90 head to use on our 70 engines is the earliest style head...96-03 maybe. The later versions have a wierd extra hole running into the head...emissions control BS I think. The extra hole can be deleted with jbweld or similar tho.
I think it's this one...says for stock trx or tb v1 heads. So maybe it's not a big dome piston.
https://tboltusa.com/store/tbparts-789-piston-54mm-114cc-for-trx90-china-90-110cc-p-423.html
The best TRX90 head to use on our 70 engines is the earliest style head...96-03 maybe. The later versions have a wierd extra hole running into the head...emissions control BS I think. The extra hole can be deleted with jbweld or similar tho.
I believe the TB piston is what I need to make this work. The deck around the dome is slightly larger than any I have looked at. I played around yesterday to see if I could trim the original piston and get what I need. I coated the surface and found the strike point. It pings on the dome near the bottom and I can’t trim that out. The other piston I have will work out when I assemble the 108 again. For now fingers crossed and waiting for the TB piston. Thanks Kirrbby for taking the time to help especially now.
The definitive answer, that's huge.
I think we can agree that, where engine building/tuning is concerned, guesswork just won't cut it.Roy Chambers
Member
If you need the Piston Machined, just mark it were you need it cut and send it up to me, and I will cut it for Free for you.
RC.
Hope to find some time this weekend to assemble the rest of the motor. The pistons vary widely. The left is long rod new dome, right is the original high compression (it has contact). These were sourced from Beatrice. The one in the middle is from TB and it is for their head. Comparing the dome to the one on the right and I can see why I had problems with the TB head having dome contact.
Roy Chambers
Member
So which one is going in? Left, Middle, or Right.
Also, what piston is in picture post # 264 ? Is that one the Left, Middle, or Right?
RC