HT bicycle engine-compatible parts

mew905

mew905

New Member
I suppose I'd compile a small list of parts compatible with our motors that arent available on any of the sites on the sides of the forum pages. These parts require little to no modifications to work.

Piston assembly

10mm Titanium wrist pin - 8.5g lighter than stock; reduces vibrations

Gilardoni silver racing wrist pin bearing - high speed, high strength bearing

46.8mm Honda Hobbit overbore piston set - **unconfirmed** Compression height of 25.5mm and overall length of 50mm, it'll need to be trimmed 2mm at the skirt but it should work in the 80mm (dax) rod 66cc engines. Sits 0.5mm higher than stock and will boost compression significantly
40mm Honda Hobbit piston set - **confirmed** - With a compression height of 26mm, using a short rod motor it will leave compression unchanged. Piston port Credit to: Jaguar

Heads and Cylinders

High performance cylinders - With a 7mm spacer, and press-fit brass bushing reamed out to 12mm, it is claimed to produce immense power. Not compatible with the Titanium wrist pin. Grubee GT5 engines only (85mm conrod) Credit to: FourEasy

Puch 70cc Hi-hi comp head - Boosts compression for more power throughout the RPM range. May need a better spark. May need to grind fins for sockets to fit. WILL need to have mounting holes enlarged and moved further away from each other.
Puch Gilardoni 74cc head - alternate head, properly sized bore. Credit to: Moto
Because of the extra thickness of the head and the fins, it's not only safe, but recommended to use the 12mm acorn nuts.

Crank

No link 6003 ball bearings - Our engines use 6202 bearings, I have seen many 50cc cranks that use 6203 bearings, which have the same I.D. as the 6003 bearings, but the 6003's will fit in our engines. This means there's a potential to use this type of bearing to fit a larger crank, However because the O.D. is the same and the I.D. is bigger, the balls are physically smaller, which means it's not as strong. 1750 Lbf for the 6202's versus 1350 for the 6003's.

No Link - Grubee GT5a Super Rat Crankshaft - Utilizing the 6003 bearings, the Super Rat crank is compatible. Small gear and magneto mount should be the same size. Crank features a 40mm stroke (2mm longer than stock), and potentially better balance. May also have a longer connecting rod.

Puch 90mm conrod - Longer-than-stock rod. Needs a press to be fit (may as well balance and true while you're at it). Gives us a 12mm wrist pin for access to more pistons.
Type D motors: 80mm conrod
Grubee motors: 85mm conrod

Intake and Exhaust

Dellorto PHBG Racing carbs - At $35 with free shipping, it's a steal. 17, 19 and 21mm sizes. Properly sized for our motors, you will need a custom intake, or intake adapter shims to fit. Credit to: Moto

YZ80 expansion pipe - **unknown mounting modifications** I know there are a couple users on this forum using this pipe, any mounting information would be helpful. Properly sized and decades of tuning experts behind it, these pipes will likely give you a huge performance boost, if you can fit it.

Electrical

12 Volt Mini-gen Max (12v generator) - alternate coil for powering lighting systems
 
Last edited:
Re: HT-compatible parts

Very nice!
That Upgrade rod bearing and titanium wrist pin looks like a great bargain hop-up combo!
Good job!
 
Re: HT-compatible parts

I'm still looking for more, in particular a compatible crank but I can't find any. They're either too big of shafts, or the rod is too long or short, or the stroke is different... plus I imagine it would have to fit the gears and magneto which wouldn't be easy either. But we have parts that can replace almost the whole motor, though admittedly not for cheap.
 
Re: HT-compatible parts

great thread - those guys at treats figured out that that con rod fits a CG because my buddy sam was experimenting with building cranks and it was somewhat of a joint experiment between him and treatland. (treatland has their warehouse like two miles from my house - its a goldmine *drool*)
 
Re: HT-compatible parts

just another addition:

this is a little nit picky but the regular puch heads have had a smaller bore than the china girl cylinder in my experience. This can be a problem when running a close gap between the cylinder and head. Solutions for this problem are either a thicker base gasket for slightly enlarging the squish of the head, either by milling or with a dremel. This issue may not apply to everyone but has been common for me. A great way to get around this is to buy this head: https://www.treatland.tv/puch-gilardoni-74cc-head-p/puch-gilardoni-head.htm

* they are temporarily out of stock but should get more real soon. This head actually has a 47mm bore! and its HUGE! which could either be a good or bad thing. It runs super cool. There is some tomfoolery involved with getting the right sized socket wrench in between the fins if your running 13 or 14mm headbolts - nothing too bad, just a little sanding to open up the fins a few mm. Just another option for those interested.
 
Re: HT-compatible parts

Moto said:
just another addition:

this is a little nit picky but the regular puch heads have had a smaller bore than the china girl cylinder in my experience. This can be a problem when running a close gap between the cylinder and head. Solutions for this problem are either a thicker base gasket for slightly enlarging the squish of the head, either by milling or with a dremel. This issue may not apply to everyone but has been common for me. A great way to get around this is to buy this head: https://www.treatland.tv/puch-gilardoni-74cc-head-p/puch-gilardoni-head.htm

* they are temporarily out of stock but should get more real soon. This head actually has a 47mm bore! and its HUGE! which could either be a good or bad thing. It runs super cool. There is some tomfoolery involved with getting the right sized socket wrench in between the fins if your running 13 or 14mm headbolts - nothing too bad, just a little sanding to open up the fins a few mm. Just another option for those interested.
Click to expand...

looks like the new fin pattern of the puch Hi hi head, but I'll add it as an alternative to the first post. And yeah, I figured all head bolts were 14mm which is... a pain to say the least with the puch heads, but the acorn nuts, as bad as people claim they are, will be a godsend at 12mm. You're right, the 14mm nuts, even using the thinnest socket I can find, are a major PITA, I have to use my socket on just the edge of the nuts or else it'll get jammed and I have to unscrew it again just to get the socket out, this is AFTER grinding the fins down (doing it with a dremel hits the harmonic resonance of the head and it gets painfully loud).
 
Re: HT-compatible parts

mew905 said:
looks like the new fin pattern of the puch Hi hi head, but I'll add it as an alternative to the first post. And yeah, I figured all head bolts were 14mm which is... a pain to say the least with the puch heads, but the acorn nuts, as bad as people claim they are, will be a godsend at 12mm. You're right, the 14mm nuts, even using the thinnest socket I can find, are a major PITA, I have to use my socket on just the edge of the nuts or else it'll get jammed and I have to unscrew it again just to get the socket out, this is AFTER grinding the fins down (doing it with a dremel hits the harmonic resonance of the head and it gets painfully loud).
Click to expand...

I use m8 12mm nuts if I can find them - they make the whole thing much easier. As far as the head its much larger than the hi hi head, ive run both on my bikes.

this is what it looks like:
null_zps9138bb34.jpg


null_zps17b1839e.jpg


IMG_6541_zpsad690543.jpg
 
Re: HT-compatible parts

Moto said:
I use m8 12mm nuts if I can find them - they make the whole thing much easier. As far as the head its much larger than the hi hi head, ive run both on my bikes.

this is what it looks like:
null_zps9138bb34.jpg


null_zps17b1839e.jpg


IMG_6541_zpsad690543.jpg
Click to expand...

That head give the bike a retro Devo look........LOL!

That thing must cool like a mad man now, also I'm looking at the carb you have on the engine and wondering what it is...?

The men this engine reminds me of... enjoy!

http://youtu.be/42qZzOMhogE


Peace, Map
reddd
 
Re: HT-compatible parts

I've been running the puch 74cc head for months. Awesome cooling and a new look. I drilled out the bolt holes 6mm to 8mm and uses head cap bolts that use a Allen wrench and took care of the problem of screwing around corners.
 
Re: HT-compatible parts

bump - added 2 more pistons to the main post

EDIT: still looking for larger intake pipes, our intake tracts look oddly similar to turbo dump pipes, I think those are our best chances at larger manifolds short of custom building (not like that would be difficult anyway). at $40 average though, I think I'd rather make one but I'll see what I can find anyway.
 
Last edited:
Re: HT-compatible parts

mapbike said:
That head give the bike a retro Devo look........LOL!

That thing must cool like a mad man now, also I'm looking at the carb you have on the engine and wondering what it is...?

The men this engine reminds me of... enjoy!

http://youtu.be/42qZzOMhogE


Peace, Map
reddd
Click to expand...

its an amal carb, great in principal - I just never really fully set it up and a dellorto ran a little better.

btw. thanks for putting the links to the dellorto phbg carbs on this list - im running a 21mm one from those guys and its great!
 
Re: HT-compatible parts

mew905 said:
bump - added 2 more pistons to the main post

EDIT: still looking for larger intake pipes, our intake tracts look oddly similar to turbo dump pipes, I think those are our best chances at larger manifolds short of custom building (not like that would be difficult anyway). at $40 average though, I think I'd rather make one but I'll see what I can find anyway.
Click to expand...

My simple trick for making an intake is to take a stock or maniac intake and epoxy a short section of handlebar to the outside of it. This brings up the OD and makes it easy to rubber mount the carb. The ID is still somewhat small, but this has not proven to be a major problem for me.
 
Re: HT-compatible parts

i have bad news. The hoca piston is a no go, iv tested on 2 cylinder and let idle the lowest it could idle for 2 mins and to be sure i didnt rev to avoid premature scoring, well i got the same results as the same cylinder, popped the head off to find major scoring. This tells me Chrome plated rings does not react well in this case. Unfortunately im 2 cylinders in the hole but confirmed this piston is not going to work :(
 
Re: HT-compatible parts

Can you change the rings? Back when I was tuning up cars in my twenties there was a local company that would make any sort of rings you wanted if you presented them with a sample piston. They didn't cost that much either.

I would imagine similar specialist piston ring companies exist in the US.
 
Re: HT-compatible parts

If never though about looking into custom rings, that sounds like a good idea. What do you think if i sanded down rings from a hit piston to fit in to the hoca?
 
Re: HT-compatible parts

Sanding down rings is something I've never tried, but I suppose if you've got the time and some spare rings to practice with you could give it a go.
 
Re: HT-compatible parts

Spare rings isn't a problem but I have 3 bad cylinders and I'm done buying them lol
 
You must log in or register to reply here.
Back
Top