Puch head on a 66cc HT bicycle engine with 6mm studs

Re: Puch head on a 66cc HT with 6mm studs

PAracer, does your piston reach the top of your jug? Im a little nervous about going down to one head gasket for fear my piston will hit the hi hi head, but I dont seem to have quite enough compression with two head gaskets, so I'm thinking of going down to one head gasket, but my piston reaches right to the top of my cylinder. Thoughts?
 
Re: Puch head on a 66cc HT with 6mm studs

Mine doen't quite make it to the top.

give it a try. Fit it up dry without a spark plug. If the piston clears when you turn the motor over by hand, you're good to go.
 
Re: Puch head on a 66cc HT with 6mm studs

Hmmm, lately I've been reading Foureasy's happy time build threads, with the moped jug, reeds, and head, and expansion chamber. I am still attracted to the bike engines because they're a good looking block and fit so cleanly compared to retrofits. It would be a nice project to build a similar engine but I wonder if it is an effort in futility. I have a broken happy time I was thinking about pulling apart to rebuild if the bottom end isn't toast.

I've read things on here about people going through many engine blocks once they figured out how to make big power with the HT engines, because they'd literally grenade. Is there anybody out there making their own strong short block assemblies with balanced cranks?

The Arrow site says that their reed block improves low and midrange power, which I'm inclined to believe because it prevents reversion and four stroking. I thought it would be a nice quick mod along with a head and a pipe on a new motor for fun versus going nuts trying to polish a turd.

Ever since I started with different motors I don't get to ride as much and it would be nice to have a happy time bike as an in-betweener. I'd like to make a crazy custom engine as a learning experience on two strokes, but in reality I need a running bike with adequate power.

I think I'll get more satisfaction out of the happy time engines if I don't have to mess with them too much, which is perhaps a paradox. Just wondering if anybody who's done all the easy power mods has to say.
 
Re: Puch head on a 66cc HT with 6mm studs

If you want a built up HT, contact Arrow. I'll bet they can build you a balanced and blueprinted engine with better bearings and some port work.
 
Re: Puch head on a 66cc HT with 6mm studs

Can some one shed some light on applications for copper spray gasket, do I spray and immidiatly install gasket & attach Puch head or spray install and waite to attach Puch head??? and can I shoot the base gasket?
 
Re: Puch head on a 66cc HT with 6mm studs

truckd said:
Can some one shed some light on applications for copper spray gasket, do I spray and immidiatly install gasket & attach Puch head or spray install and waite to attach Puch head??? and can I shoot the base gasket?
Click to expand...

Spray it on both sides and let it get tacky to almost dry. About 15 minutes in warm weather and longer the colder it is. Lean it against something so nothing touches the surface. I've used it to seal up cylinder heads on my race motors and never had a failure. Race motors as in circle track late model/light 151 Pontiac motors at 12.5:1 ratio. I use better bolts on them, too. Did you get the head stud kit from sick bike parts? It's the best way to go.

As far as the base gasket goes you can but it can act as a glue and if you have to seperate the parts down the road you will most likely have to scrape the crap out of the gasket to get it off. I used Hi Temp silicone RTV gasket maker thinly smeared on both sides of the gasket. Seals great and you can generaly get the parts apart without destroying the gasket.

brnot
 
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Re: Puch head on a 66cc HT with 6mm studs

Actually got 8mm Allen bolts at a local precision nut & bolt specialty shop, can I get the base gasket as well and what is torque on the bolts??
 
Re: Puch head on a 66cc HT with 6mm studs

Yah, you can get base gaskets on eBay no probs. 12 ft pounds of torque. Your going to have problems with a 14 mm socket for the 8mm nut, though. There's no space for it between the fins. The sick bike parts nut is 13mm so there's room to get the socket in. Some have ground the fins in the socket area to fit the socket down over the nut. Some have said you can get a thinwall 14 mm but I don't know where to get it, might be some Snap-On socket or something :p

Allen bolts, didn't see that. If you have a 8mm tap I'd run it down the holes. The Chinee sometimes take a shortcut and not tap them to the bottom.
 
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Re: Puch head on a 66cc HT with 6mm studs

The bolts are allen bolts with an allen socket that is tappered at the bottom, slides right in no problem, the bolts will have flat washer combined with lock washer, I've had it tightened down (not torqued) kinda dry run and everything seems to be in order .
If something does or doesn't happen the way it should or shouldn't happen I'll jump right back on this thread.
Thanks! for the info Dave
 
Re: Puch head on a 66cc HT with 6mm studs

I'm thinking I might go this route soon. I like that you can eliminate the gaskets if you use this head, because they're a source of failure. It seems that the bottom end rod bearing and crank problems are troubling so I think I'll do a total rebuild to correct all the bad assembly that makes the cranks junky. I have a PK happy time that I think I ruined the rod at the piston from running at sustained top speed, maybe if it's good inside I'll use that as a base, although I am tempted to start new because I don't trust the fatigue endurance of any of the HT parts, or casings.
 
Re: Puch head on a 66cc HT with 6mm studs

I just received and installed my puch 70cc hi hi head today on my 66cc bike. I have the 8mm studs so i just took a drill and ported the holes to fit. also used 2 puch gaskets that i ordered from treatland (stud holes also had to be ported to fit). these gaskets were .4mm thick. No contact with piston/head/spark plug! Also put a ngk B8HS plug in. My bike doesnt have a choke so its always a pain to get started and warmed up when it is cold, so i aimed it down a small hill by my house and started peddling. Soon enough had it up and running! Low end torque seems to have increased drastically! If i was to slow on a hill before and try to regain any momentum i would have to peddle. With the head swap...slowed down then got back on it and it started to pull up the hill without any help! Cant say as far as top/mid range power just yet because havent really gotten it out (drizzly and this was all at night), but all it is seeming that this is a great mod for the money!
 
Re: Puch head on a 66cc HT with 6mm studs

Oh, and i had already replaced the acorn nuts with 13mm hex bolts i got from home depot. otherwise clearance with this head would have been a pain!
 
Re: Puch head on a 66cc HT with 6mm studs

Excellent job on the head swap! Glad you liked the results. Did you try with one gasket? If the piston clears, the compression will bump a bit more and you will have even better performance.
 
Re: Puch head on a 66cc HT with 6mm studs

Can you share a pic of the puch head gasket I bought one and it has a funny shap to it, extra bolt whole in front of the gasket but a pic to compare would be cool!
Thanks!
 
Re: Puch head on a 66cc HT with 6mm studs

PAracer said:
Excellent job on the head swap! Glad you liked the results. Did you try with one gasket? If the piston clears, the compression will bump a bit more and you will have even better performance.
Click to expand...

Thanks! I was thinking about that, but these gaskets are 1/2 the thickness of the ones that came with my grubee, I'll have to check if it clears one of these days! :D

truckd said:
Can you share a pic of the puch head gasket I bought one and it has a funny shap to it, extra bolt whole in front of the gasket but a pic to compare would be cool!
Thanks!
Click to expand...

Those are the gaskets I used too, I'll snap a pic soon. They seem to seal just fine. I just pointed the weird spare hole to the side, no reason to it at all.
 
Re: Puch head on a 66cc HT with 6mm studs

These are the gaskets I used.

The head installed


And my project bike that its on :)
 
Re: Puch head on a 66cc HT with 6mm studs

k.mah said:
Thanks! I was thinking about that, but these gaskets are 1/2 the thickness of the ones that came with my grubee, I'll have to check if it clears one of these days! :D
Click to expand...

I currently am not using a head gasket on my Grubee. I did have to double up on my spark plug gaskets to maintain plug clearance. You'll have to check clearances as you button the motor up. First, assemble it without a spark plug. Rotate the motor over to see if the piston hits the head. Then, after clearance is verified, try it with the spark plug installed. Rotate the motor over slowly a couple times. Pull the plug and see if you still have clearance. Be sure to use a bit of copper gasket maker.
 
Re: Puch head on a 66cc HT with 6mm studs

PAracer said:
I currently am not using a head gasket on my Grubee. I did have to double up on my spark plug gaskets to maintain plug clearance. You'll have to check clearances as you button the motor up. First, assemble it without a spark plug. Rotate the motor over to see if the piston hits the head. Then, after clearance is verified, try it with the spark plug installed. Rotate the motor over slowly a couple times. Pull the plug and see if you still have clearance. Be sure to use a bit of copper gasket maker.
Click to expand...

No head gasket with the puch head?
That's awesome! I can only imagine how much torque it has!
Is there a point of diminishing return with the compression?
I guarantee I have room to increase mine, but how much would be too much (basically how close should i try to get to the head without touching before its just chasing my own tail?)
 
Re: Puch head on a 66cc HT with 6mm studs

Also, are you using a cylinder body bottom gasket? (cant think of if that's the correct term for it, but i'm sure you know which one i'm referring to)
 
Re: Puch head on a 66cc HT with 6mm studs

I do have a base gasket. The same one that I started with. I wouldn't want to go without it. That would affect the port timing, and also I don't trust the sealing surface of the crank case.

As far as compression goes, more is better. There is a point though where it puts too much pressure on the bearings, and too much stress on the ignition system. In my case, my motor isn't quite broken in yet. I haven't run a full gallon of fuel through it. I have since put the bike away for the winter.
 
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