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

[maurtis]

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

Maurtis where do you get the wrist pin bearing ? as I don't want to order another crappy one from a Co. that sells the same engine kit and since I already have mine apart why not? just go ahead and do it, what is it exactly called as far as size and or part number bearing, sorry for the questions but I do believe it's refrred to as R&D (LOL) Thanks! for the help.

I have a bearing place nearby, I am going to check with them first to see if they have a Japanese bearing that fits.

There are a ton of threads on the size and where people get them, here is a recent one: The bearing doctor!!!

It sounds like a good plan to go ahead and change it out if you already have the engine apart. Good luck!

 

[truckd]

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

Well the puch head is on the way and I also ordered a 10x14x15 wrist pin bearing but now every one is talking about running washers on both sides of the and in between the boss's how does that inneract with the bearings and the boss's won't that wear out the bearing and ping as well, I'm begining to feel like I've opened a can of worms ,give me some incouragement!!

 

[culvercityclassic]

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

I would just install the head and run it. You guys should be ok. I run the 50 cc head with one gasket on two bikes with no problem, Headtrama does the same on two bikes. Replace the bearing since you already ordered it.

 

[truckd]

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

Thanks for the info! much help! runn'n a PK 68.5/80cc

 

[maurtis]

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

Got a wild hair last night and went from two head gaskets on my 70cc head to one. Turned the motor over by hand and did not hear any clatter, so seems like there is clearance. It was too late to go for a test run, so waited until after work today.

WOW, holy compression Batman! Yeah... my clutch was always on the soft side and would slip occasionally with the stock head. It did not even come close to turning over the 70cc hi hi head with one head gasket, lol. It just slipped and slipped and I pedaled furiously, maybe turning over about 1 revolution per second. That was some really good exercise, though!

I had been meaning to tighten my main clutch spring, so now is the time. It will be interesting to feel how the extra compression will affect the power. Going from the stock head to the Puch head with 2 gaskets gave a good torque bump, so if I can get the engine to start, should be a blast!

 

[maintenancenazi]

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

Got a wild hair last night and went from two head gaskets on my 70cc head to one. Turned the motor over by hand and did not hear any clatter, so seems like there is clearance. It was too late to go for a test run, so waited until after work today.

WOW, holy compression Batman! Yeah... my clutch was always on the soft side and would slip occasionally with the stock head. It did not even come close to turning over the 70cc hi hi head with one head gasket, lol. It just slipped and slipped and I pedaled furiously, maybe turning over about 1 revolution per second. That was some really good exercise, though!

I had been meaning to tighten my main clutch spring, so now is the time. It will be interesting to feel how the extra compression will affect the power. Going from the stock head to the Puch head with 2 gaskets gave a good torque bump, so if I can get the engine to start, should be a blast!

Always good to try new things! I was wondering if you had thought about adding an additional base gasket to the case? Not just for more compression, but also to raise the transfer ports slightly. There have been many rumblings over the years about slightly raising the jug to alter port timing. Apparently these engines are said to benefit from this. Just a thought...
Peace, James

 

[biknut]

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

I finally got my NGK BR9HIX spark plug in, which was the last piece I was waiting for to install the new head. I was shocked that I could not find one locally, so I ordered 2.

With the BGF RB80 motor, which I am pretty sure is the same as the Grubee GT5a with 6mm studs, the Puch 70cc hi hi head fits perfectly, I did not need to modify it at all.

I test fit the head without any head gaskets, just to make sure that it would go on, and I verified that the piston will hit the head without the gaskets. I had ordered two new head gaskets for the 6mm 66cc motor from SBP and already coated them in spray copper gasket maker, so I slipped on the gaskets, put on the head, then tightened up the head nuts in a Z pattern.

Unfortunately the only torque wrench I could find that goes down to inch pounds uses the smaller drive, what is it, 1/4"? And my 10mm socket that fits is was too short, so I had to tighten them by feel using my longer 10mm socket on my "regular" socket wrench. So this evening I need to go out and see if I can either find an extension to fit the socket, or preferably a deep socket.

Oh yeah, and I switched to 93 octane a few days ago in preparation for the new head.

Riding impressions: love it! I was afraid my clutch was going to slip, but she fired right up. Noticeably more torque down low and mid range and the engine noise seems a tad less raspy. Usually if I let the clutch out around 10 MPH (this is with a 36 tooth sprocket), I still have to pedal quite a bit to get my 195 lb self going. With the new head, from 10+ she pulls on her own

I really am not sure about the high end since I think my CDI is unhappy. With the stock head I would start getting what sounds like pinging in a series of machine-gun style spurts starting around 33 MPH, which would kill the power. I could get her up to 37 MPH, but she tops out around there, which feels limited by the pinging. I was hoping going to 93 octane would help, but nope. I get the same behavior with the Puch head, except I get there faster

My Jaguar CDI should be here next week, so we will see if the CDI really was the culprit...

Are you sure it's pinging, or do you mean 4 stroking?

 

[maurtis]

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

Are you sure it's pinging, or do you mean 4 stroking?

After backing my jetting down from a 72 -> stock -> 68 and having it go away, I am definitely thinking it was 4 stroking! The reason I ruled that out earlier was because it sounded different than what happens when I have my needle clip too rich, and different than the youtube video posted on this forum about "what does 4 stroking sound like", and my plug was a nice chocolatey brown.

BUT, at a 68 jet I now only get it at WOT during the first few minutes of a ride, then it goes away, so thinking now that it was just 4 stroking the whole time.

I was able to get in a good, long ride at the 68 jet with no 4 stroking, almost hit 39 MPH. But then I got ballsy and went to 1 head gasket and now my clutch slips, my gas tank broke, I still need to replace a leaking crank seal, ran out of beer, dog ran away...

(kidding about the dog, he is too fat to run away)

It will be a busy weekend for me and the MB, but we will both be better for it at the end.

 

[biknut]

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

Thanks for explaining that. I was wondering about that because I have yet to hear any pinging from any of my MBs, but 4 stroking is pretty common.

 

[maintenancenazi]

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

Thanks for explaining that. I was wondering about that because I have yet to hear any pinging from any of my MBs, but 4 stroking is pretty common.

^ It's kinda weird, it seems more and more people these day's are hearing some kind of pinging/detonation ( Me included ) from these little mills. In fact two, out of three engines, all from BGF have done this ( slant heads ). That is one of the reasons I started running a colder plug than most. Seems to help alot, but does not eliminate it completely, even with premium gas... weird, just weird....

 

[biknut]

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

^ It's kinda weird, it seems more and more people these day's are hearing some kind of pinging/detonation ( Me included ) from these little mills. In fact two, out of three engines, all from BGF have done this ( slant heads ). That is one of the reasons I started running a colder plug than most. Seems to help alot, but does not eliminate it completely, even with premium gas... weird, just weird....

I think a lot of people are confusing piston ping, with 4 stroking.

These motors don't have enough compression to really want to ping very much. My last 2 motors were from BGF/Rico Group. 1 of them was running a MM high compression head, and adjustable rotor, advanced. I always run regular gas. All my motors are running NGK B5 or BP6. I've never run anything else. So far I've never noticed any pinging.

 

[maintenancenazi]

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

I think a lot of people are confusing piston ping, with 4 stroking.

These motors don't have enough compression to really want to ping very much. My last 2 motors were from BGF/Rico Group. 1 of them was running a MM high compression head, and adjustable rotor, advanced. I always run regular gas. All my motors are running NGK B5 or BP6. I've never run anything else. So far I've never noticed any pinging.

Oh boy where to start. I can most certainly attest this is NOT 4 stroking! If it were 4 stroking this issue would go away, or at least reduce when one leans the mixture. Instead this pinging ( sharp metallic rap ) only gets worse when you lower the needle, or lean it out in any way. But when you raise the needle enough ( richer ) it will go away. totally opposite of what SHOULD happen if it were just overly rich from 4 stroking.

I have built and tuned many different engines, motorcycles, RC aircraft, street supercharged V8s with over 700 HP, and many small engines both 2 stroke and 4 stroke since 1979. So ( at least in my case ) I can say it isn't 4 stroking. That's why a say it's weird, because as you said yourself very correctly, these little engines come with really low compression, so much so they should NEVER need high octane fuel. But every time I would treat the symptoms like it is pre-ignition/detonation it had positive effects ( reduction ) in this sound, whatever it may be!!

Peace, James

 

[truckd]

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

Ok! Puch Head got here the other day and it looks like the bolt holes are to narrow now what do I do? people talk about drilling them them "it's soooo!! easy, ya right! nothing is easy about these China girls (unless you are the guy slapping them together in China) and all I have is a Dewalt cordless whaaa!!!

 

[maurtis]

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

Tightened up my clutch last night and went for a ride today, WOW. the torque bump from 2 head gaskets down to 1 is great, LOVE it. My clutch is much harder to pull now, but I guess that makes it normal, lol.

Time to work on my clutch roller project, or also considering getting a motorcycle clutch lever assembly since the lever is longer for more leverage, and it will have a mirror perch built in, like these:

 

[maurtis]

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

Ok! Puch Head got here the other day and it looks like the bolt holes are to narrow now what do I do? people talk about drilling them them "it's soooo!! easy, ya right! nothing is easy about these China girls (unless you are the guy slapping them together in China) and all I have is a Dewalt cordless whaaa!!!

You must have the 8mm studs then, right? It just slipped right on to my 6mm studs.

I am sure you could take your stock head and the Puch head to a machine shop and have them hit it with the drill press. For such an easy job, they should not charge much. Or just trust your steady hand with the cordless drill!

 

[truckd]

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

I have a 1936 Harley Davidson clutch lever and perch on Ol' blue( thread located at motorized cruisers title'd "Ol' Blue" pg 8) and even set it up with the stop hold buttonto hold the clutch in, like the Chinee did, but getting back to the cables you'll have to make a bigger cable stop to accomedate the larger stop hole in the clutch lever and remember DON'T! use a stainless steel cable, the sodder won't hold to it. In fact the bike is in the avitar top left corner
How many gaskets are you using ? on the Puch head

 

[maurtis]

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

I have a 1936 Harley Davidson clutch lever and perch and even set it up with the stop hold buttonto hold the clutch in, like the Chinee did, but getting back to the cables you'll have to make a bigger cable stop to accomedate the larger stop hole in the clutch lever and remember DON'T! use a stainless steel cable, the sodder won't hold to it.
How many gaskets are you using ?

Yeah, I found that out the hard way, when trying to solder the end of my current clutch cable to keep it from fraying since I was taking it on and off a lot to adjust my clutch spring tension. I was fairly drunk at the time so just assumed it was something I was doing, lol!

I am running just one head gasket now, WOW! I had to tighten my clutch spring tension quite a bit to get it to not slip while starting, but the extra torque is very nice.

 

[truckd]

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

Its not not my steady hand that concerns me it's my off set eyes.
Use an eye dropper and put some good lubricant in it, then squeze it into the cable housing until it comes out the other end keeps the cable from rusting and beleive it or notthe lubricant keeps the cable braid taunt( not! tight, thats on you)

 

[fx-2]

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

Got my head today . All ready opened the stud holes . The motor apart , ported the cylinder . Just need time now , got one on bench now . when it's done I'll start mine . Dan

 

[truckd]

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

FX did you use a drill press? them bores look awful pretty! I'm waiting on my stock PK80 head gasket and new wrist pin bearing