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

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

PAracer said:
I just received a package of mounting hardware for my M8-1.25 stud Puch head.

Purchased from Mcmaster
p/n
91290A414 M8-1.25 socked head screw 10mm long class 12.9
93020A781 M8 coupling nut 19mm long
98035A105 metric extra thick washer
91458A560 loctite 262 red

I also used anti-seize on the studs.
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Let me know how this all works out for you.

I had no issues with installing the 50cc head with one gasket, matter of fact I used the old one...laff No need to change to any fancy hardware, and you should stay away from red loctite, blue is what should be used if any.

I raced this bike in the last race, dead of heat wide open with no issues. I did have race gas in the bike tho...
 
Re: Puch head on a 66cc HT with 6mm studs

PAracer said:
The mass of the head is at least double that of the HT head. I can weigh them both after work today. That added mass directly affects the cooling capacity of the engine.
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Ok. I weighed the heads.

Stock 66cc slant head is 259g

Puch 50cc hi hi comp head 578g

All else equal, a heavier heatsink will be more effective than a lighter heatsink. Of course, not all else is equal. However, I have a feeling that the Puch head is better in those respects as well.
 
Re: Puch head on a 66cc HT with 6mm studs

culvercityclassic said:
Let me know how this all works out for you.

I had no issues with installing the 50cc head with one gasket, matter of fact I used the old one...laff No need to change to any fancy hardware, and you should stay away from red loctite, blue is what should be used if any.

I raced this bike in the last race, dead of heat wide open with no issues. I did have race gas in the bike tho...
Click to expand...

I hope it works out too:)

I chickened out and put two gaskets in there. I have the socket screws held into the coupling nuts with red loctite because I want them in there for good. If the socket head screw came out, I would be in trouble with an unreachable nut. The couplers are anti-seized to the head.

picture.php

Once I get this thing running, I'll take some nice, clear outside shots.
 
Re: Puch head on a 66cc HT with 6mm studs

Just a heads up if you guys are running ngk iridium, iridium plug is longer than normal ngk if you have not noticed.
 
Re: Puch head on a 66cc HT with 6mm studs

PAracer said:
I hope it works out too:)

I chickened out and put two gaskets in there. I have the socket screws held into the coupling nuts with red loctite because I want them in there for good. If the socket head screw came out, I would be in trouble with an unreachable nut. The couplers are anti-seized to the head.

picture.php

Once I get this thing running, I'll take some nice, clear outside shots.
Click to expand...

thats the biger engine right ?

dose the piston hit the head with 1 or no gaskets ?.wee.
 
Re: Puch head on a 66cc HT with 6mm studs

I started with two gaskets. I removed one this evening, but I haven't had a chance to take a ride.

This is a 66cc engine I'm working with.
 
Re: Puch head on a 66cc HT with 6mm studs

Ok Guys here is the skinny on the Indian Engine............
PK 69.5/80cc Engine
70cc Puch Hi Hi comp head
Delorto 15mm Carb
S/S Sportsman Flyer Intake Tube with matched port flange
Performance Racing Expansion Chamber Exhaust Pipe
Jaguar CDI & Coil
CR Mmachine Man Modified piston
High Qaulity Wrist Pin Bearing and Crank Bearing
Ported Exhaust & Intake and re-surfaced Deck on Cylinder
Laser cut Head and Cylinder Gaskets
How many Head Gaskets am I supposed to use? there has been much debate about 1 or 2 when I put this baby together I don't want to take it apart so my four and most Important questions are..
How Many Gaskets?
What Spark Plug, NGK BP7HS or BP8HS ?
And if any one is using a Delorto 15MM Carb what Jet size
What is the correct torque on the Head Bolts(again a widely debated subject)
Pool the knowledge and pay it forward (LOL!) but seriously need all the knowledge I can get to do this right the first time.
PA racer why? did you delete a gasket, did you run the engine and didn't get good compression ?
Thanks! Guys
 
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Re: Puch head on a 66cc HT with 6mm studs

That's a long list of items for that motor, I sure hope it runs good. I know someone will chime in with some support.
 
Re: Puch head on a 66cc HT with 6mm studs

I have not had a chance yet to run the motor. Perhaps I will tonight if the weather clears up.
 
Re: Puch head on a 66cc HT with 6mm studs

It runs... with one gasket that is. No trouble starting.

I think i have an air leak at the carb seal. I'm going to see what I can do with that this evening if I'm still alive at that point. I've been up since 1am, and I'm starting to feel like it.
 
Re: Puch head on a 66cc HT with 6mm studs

Okay, this bike is starting to wake up. I've probably got 5 or so miles on it just running up and down my back alley, around the block, and through the yard. This evening, out of nowhere, the bike picked up a bunch of mid range, and top end power. It now goes too fast for my street:)

I did goo up the carb/intake union. I'm also figuring out the idle speed and idle mixture screws. I might just try to figure this CNS v3 carb out.
 
Re: Puch head on a 66cc HT with 6mm studs

Last night I pulled out the last of my head gaskets. No piston/head contact! I'm gonna see if it wants to start tonight. Either me or my next of kin will provide an update later.
 
Re: Puch head on a 66cc HT with 6mm studs

PAracer said:
Last night I pulled out the last of my head gaskets. No piston/head contact! I'm gonna see if it wants to start tonight. Either me or my next of kin will provide an update later.
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A gasket isn't just to adjust the compression, it's needed to seal the mateing surfaces. It's made of what is called dead soft aluminum. I'm betting you get black crud comeing out from between the head and jug. Let it go on too long and the hot gasses can actually cut a hole. It's called torching, as in oxy/acet torch.

Use a gasket, save yourself some grief.usflg
 
Re: Puch head on a 66cc HT with 6mm studs

It may not even make it thaat far. :) So far, the compression seems to have loosened the screw holding in the small bevel gear.

I keep a pretty sharp eye out for leaks. Heck, I drove a land rover. Those leak more than a scrren door on a battleship.
 
Re: Puch head on a 66cc HT with 6mm studs

So far so good. I cleaned up my spark plug, and closed the gap a smidge. The bike started right up. It does slip the clutch for a brief second before it kicks over.

I don't know if it had any more oomph, but I did tackle the steepest hill in my neighborhood for the first time. It's one of those hills where one side of a house is ground level, the other end is in the basement. It did pretty good, I pedelled a bit, but the bike was picking up speed the whole way.
 
Re: Puch head on a 66cc HT with 6mm studs

PAracer said:
So far so good. I cleaned up my spark plug, and closed the gap a smidge. The bike started right up. It does slip the clutch for a brief second before it kicks over.

I don't know if it had any more oomph, but I did tackle the steepest hill in my neighborhood for the first time. It's one of those hills where one side of a house is ground level, the other end is in the basement. It did pretty good, I pedelled a bit, but the bike was picking up speed the whole way.
Click to expand...

This is what I like to hear. I just installed the hi hi head, but haven't driven it yet. I am hoping for more torque, and your update is encouraging me.
 
Re: Puch head on a 66cc HT with 6mm studs

I think you're going to like it. I hope I get to ride this weekend. I keep going a bit further each ride.
 
Re: Puch head on a 66cc HT with 6mm studs

How many HP are we talking about if you were to put a Puch Hi Hi, an expansion chamber, and a Arrow reed block on a 66cc happy time? Can the engine handle the power increase? I'm interested because I love the looks of the china girls but want one that isn't a slug, something that can take off from a stop.

These mods like revs, in that case spinning up the motor before applying power is good. I think a centrifugal clutch setup might be the way to go on this, with a pull starter. The HT manual clutches are weak, and slip. When you allow the motor to spin up free from load it can build momentum and therefore apply more starting torque.

If the china girl pull starters are junk then maybe a Kevlar cord could help. People always say the cord snapped, while that is common with all pull starters with weak cord.

I really don't want to give up on the HT's, and would like to build a nice custom one for a cruiser, rebuilding while new to make sure it's not full of shavings and loose bolts. The biggest problem I had with mine was that it lacked power because you have to engage the clutch so early, so you gotta drive a two stroke like a four stroke and bog it out. Maybe there's a centrifugal clutch with high performance orientation that will fit an HT?

Getting rid of a clutch lever makes it so that you can allow friends to ride your bike without having difficulty and messing the clutch up, especially important as a pit bike for friends and family. If the bike actually had selectable gears I'd say the manual clutch is worth it, but with only one it just makes consistent engagement a pain. I originally thought it might be neat to have a manual clutch on a Cag pocket bike engine before I read about the advantages of the centrifugal clutch.
 
Re: Puch head on a 66cc HT with 6mm studs

I don't have a reed valve, but from what I understand, you need to port the heck out of the jug and passages to take advantage of it. If you go through with all of it, you will have a potent little mill. Balance the crank and you will be able to get a few more revs out of it as well. I would suggest upgrading your bearings, wrist pin, crank, etc.

I can't tell you if the head makes a big difference over stock. I never even tried the stock head. The SBP expansion chamber did make a noticable difference. The sprocket adapter, #41 chain and 36 tooth was also a wise upgrade.
 
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