Puch Moped Head on HT 67cc bicycle engine- thanks Foureasy!

Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

Be aware that the squish clearance will have to be checked on any of these puch heads. On top of that, lapping the head and mating surface on the cylinder makes a world of difference.
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

Kristof said:
Which one?

Hi Hi head without O-ring

or

the one with the O-ring

Would red High Temp RTV silicone work if need be?

What kind of spark plug does this take?
Currently I have an NGK B5HS
Click to expand...

I used the one without the o-ring,

RTV should never be used as a head gasket,

There will be a lot of variables, but I personally needed to run a much colder plug than stock to prevent ping. Ended up running a B10HS....

Peace, James
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

So apparently it has the same thread and length that the stock head have, correct?

What octane fuel are you using? Did you try using octane booster?
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

I know every motor is different, but I run my 66cc "RB80" and 70cc Puch head with one head gasket, 93 octane and an NGK B6HS with no pinging. I get a little 4 stroking for the first mile or so, but once she warms up she is clear as a bell all the way up to 39.8 MPH. Sooo... close... to... 40... need... to... lose... weight... LOL

I do run a Jaguar CDI, though, so maybe changing the timing curves helps too?
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

^^ Maurtis and myself purchased the same exact head. That's where the similarities end. Whether or not one has preignition/detonation, can be quite a " rabbit hole " me thinks.

Variables such as, rider weight, final gearing, local elevation, ambient temp, hills or flat land, and minor differences in engine configuration can all determine whether one encounters this or not.

Bottom line, every installation is different. So it is up to US and us alone to dial in and tune our engines to adjust to these variables. experimentation is a must!
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

Kristof said:
So apparently it has the same thread and length that the stock head have, correct?

What octane fuel are you using? Did you try using octane booster?
Click to expand...

To answer your question, yes spark plug reach is the same as a stock head.

And yes, I AM running some octane booster, as well as the cold plug.

I am a big heavy human, weigh 230lbs, plus most all my riding is in the mountains of Western NC, lots of hills, not much flat land. Plus I run a 32 tooth rear sprocket, this loads/heats up the engine quite a bit hauling my big a#$ around! The engine has plenty of torque with my upgrades to do this, it just heats up real quick, especially now in the summer heat. Hope this helps...

Peace, James
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

I would like to know what head gasket to use because the stock head gasket is a smaller inner diamiter then both head and cylinder/jug also found some thinner aluminum material half the size of the thickness of stock gasket, I was thinking about using the spray copper gasket sealer to marry the two incase the one stock gasket is not enough and two is too much, give me some feed back on both situations
Thanks all!
Oh! and by the way I'll be running the 70cc Hi Hi comp head without O ring, fully ported cylinder, Dellorto carb 15.15 and a performance exhaust pipe on a PK 68.5/80cc engine 40 t rear drive sprocket I weigh 200lbs
 
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Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

I've said it before, and I'll say it AGAIN. Lap BOTH mating surfaces with 600+ grit sandpaper on a piece of plate glass.
Dry fit your top end together, and check your squish clearance with a piece of rosin core, lead based solder. Squish should be No Greater than .030" Measure with accurate calipers/micrometer.
Shim up or down squish clearance with thicker/thinner base gaskets.
Clean all mating surfaces with alcohol or brake cleaner, and assemble head to Cylinder with a VERY light coat of Ultra Grey silicone. You're going to argue that it says right on the tube not to do this. That's so morons don't do it. If you're Smart, you'll realize that lapping the cylinder and head Flat is what's doing most of the sealing. The silicone is mostly there to adhere the head to the cylinder, and provide extra sealing.

Torque it all down and let sit overnight. Check torque before riding. You shouldn't need much more than premium gas for this head IF squish clearances have been set properly.
The head has much better cooling than the stock heads, and the Squish design retards the tendency for end gases to detonate, even under the additional compression.

Expect to see an increase in Low to midrange power. It's also possible that overall power will go up drastically, as the combustion chamber shape is idealized, and promotes a total burn much more quickly than the stock chamber. This essentially 'Builds In' Ignition advance without the negatives associated with advancing the ignition.

DON'T FORGET TO RE-JET.
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

maintenancenazi said:
To answer your question, yes spark plug reach is the same as a stock head.

And yes, I AM running some octane booster, as well as the cold plug.

I am a big heavy human, weigh 230lbs, plus most all my riding is in the mountains of Western NC, lots of hills, not much flat land. Plus I run a 32 tooth rear sprocket, this loads/heats up the engine quite a bit hauling my big a#$ around! The engine has plenty of torque with my upgrades to do this, it just heats up real quick, especially now in the summer heat. Hope this helps...

Peace, James
Click to expand...

Cant believe youre running a 32, i have a 36 and its perfect to go to 40mph.
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

Kristof said:
Cant believe youre running a 32, i have a 36 and its perfect to go to 40mph.
Click to expand...

Well actually I was trying lower gears to be able to lower cruse rpms. Just couldn't stand the sound of that little HT screaming it's guts out to go 25 mph.

I also tried a 36 toother, was an improvement, but still felt like it could pull an even taller gear. Installed the 32, and never looked back! Cudos on the new head, I think you'll like it!

Peace, James
 
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Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

Does the punch head come with a head gasket ? or do i need to order one
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

I'm told that the stock gasket is used but it looks like the center opening is a little small for the jug, like the piston is going to hit it
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

desolation said:
Does the punch head come with a head gasket ? or do i need to order one
Click to expand...

It does not, so you will want to order an new one, or two. Some people run 2 head gaskets, which gives you less compression but makes it easier to start the motor. Also, I think some piston crowns are shaped a little differently, so might need the extra space?

I started with two head gaskets to be safe, then went down to one. Definitely an added bump in torque, but my clutch slips quite often when trying to start the bike now. I will probably try to tighten the internal clutch spring a little more this weekend...
 
Re: Puch Moped Head on HT 67cc motor- thanks Foureasy!

Ok, I would say after my initial tests it has around 50% more torque with my setup. (I will update my build thread one day with pictures.)
I was using old 91 octane fuel with approximately 100:1 ratio of Opti 2 and an NGK B5HS plug with Jaguar CDI.
 
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