Stage 2 Video 47.5 Mph Top Speed

[210061741]

Don't worry.
Just gonna be a wile before i can fund everything.
But i have some good things in the works.

Just trying to offer you a solution.

Other than waiting.

 

[thuginfc]

Rich, don't be too fussed about the opinions of others.
People who rely on a motored bicycle to be reliable as daily transport are counting on you to make a high quality product, and i'm one of them.

Fabian

i have been following the workings of 2100##### and it seems as he knows this engine inside and out

i use my motor bike as my only daily ransport cause i have no license (as it saddens me to see a perfectly good icy cadillac sit in the garage everyday)

ive been awwaiting a good quality motor for some time now and if it can be donw with a HT + some parts im all down for it

need more power more speed more more more!!!!!!

also i asked in another thread with no real reply will the puch 70cc head bolt right onto a stock cylinder? no milling or anything?

 

[210061741]

Hi Thuginfc

I am pretty sure i did reply to your question about the head.
It will bolt onto any 66 / 80 cc HT engine.

The holes in the head are for 7mm studs and they need opened up a tiny bit.
If you put a broken round file in a drill it works great.

Other than that it is a direct bolt on.

It is a goodupgrade for $30.00

http://www.treatland.tv/puch-moped-70cc-hi-compression-head-p/puch-hi-comp-head-70cc-maxi.htm

 

[210061741]

As far as making the HT engine reliable.

That's a tough thing to do.

I have done everything possible to make them better.
It is easy to get higher speeds and more power.
The head and a ported cylinder accomplish that.

But reliability is still an issue. I have used quality bearings and great care in assembling the engines yet i allways seem to find a weak link in the chain.

Recently i have had alot of issues snappin the piston wristpin in half after the small end needle bearing fails. The bosses that hold the pin in the piston are weak, and there is a great deal of clearence between the bearing / Conrod / and wristpin.

I believe this is causing the needle bearing cage to get eggshaped due to the clearence.
The wristpin is constantly hammering the bearing back and fourth distorting the shape and causing seizure. Upon seizure of the bearing it places an extreme load on the wristpin causing it to break.

I have approximatly 1000 miles on my lone wolf build.
I snapped the wristpin once around 700 miles.

I replaced the piston and the wristpin and the needlebearing.
I used a very high quality needle bearing and 300 miles later it's ready to give again.

I used top quality mainbearings and there also worn badly.

The engine quit running on me yesterday so i think im going to rip it apart and see what damage has been done. My guess is alot.

Now if you make all the upgrades and baby the engine, really baby the engine it will last longer. But thats no fun. Iv'e been running a 40T sprocket and average RPM of 6000 to 8000. It has a real nice power band and pulls hard from 0 to 40 mph. But to get more than 1000 miles before a rebuild i think is alot of luck.

Running a 34 or 36T sprocket would be better. But you give up the quickness the engine has. The top speed goes up in the 50 MPH range but it takes longer to get it movin that fast. The smaller sprocket keeps the engine in the lower RPM range so it will last longer.
It seems that spinning the engine much more than 6000 rpm causes the small end needle bearing damage. The bearing im using is rated for 21000 rpm but the excessive clearence causes damage.

 

[thuginfc]

i havent upgraded any bearings in mine (yet) but plan on replacing them when i do my new bike but i run mine to 7400 all the time havent went much past that cause im scared the bearings will start failing...

thanks for answering bout the head also will the puch cylinder and piston fit?
is the bottom of the puch cylinder flat or does it protrude into the crankcase?
i would probably have to do some port matching huh?

 

[thuginfc]

also i use a 36 tooth sprocket..

 

[SaxAnton]

As far as making the HT engine reliable.

That's a tough thing to do.



Recently i have had alot of issues snappin the piston wristpin in half after the small end needle bearing fails. The bosses that hold the pin in the piston are weak, and there is a great deal of clearence between the bearing / Conrod / and wristpin.

I believe this is causing the needle bearing cage to get eggshaped due to the clearence.
The wristpin is constantly hammering the bearing back and fourth distorting the shape and causing seizure. Upon seizure of the bearing it places an extreme load on the wristpin causing it to break.

I have approximatly 1000 miles on my lone wolf build.
I snapped the wristpin once around 700 miles.

I replaced the piston and the wristpin and the needlebearing.
I used a very high quality needle bearing and 300 miles later it's ready to give again.

I used top quality mainbearings and there also worn badly.

It seems that spinning the engine much more than 6000 rpm causes the small end needle bearing damage. The bearing im using is rated for 21000 rpm but the excessive clearence causes damage.

IMHO the clearance of a pin <>conrod<> piston is never the cause for your sort of problem. In a good alligned engine it the conrod 'finds' its place without going sideways.
Too little oil/overheating is possible, but in Chinese motors I suspect it has probably more to do with faulty allignment of some parts to each other, ie
Bent conrod, or maybe the cilinderbore is not at square axis to the crankshaft.

you can check the crancase and conrod by placing a piece of silversteel (drillrod?) of the same size as the pistonpin, but longer, in the small-end, check if it is level on each side of the crancase where the cilinder sits.

If it is not level, you have the problem that is more likely to be the cause of the trouble you describe than the 6000 revs on a GOOD bearing.

 

[Fabian]

Interestingly, i've never had a wrist pin bearing or bush fail, in all 5 of my engines, and i suspect 20:1 oil/fuel ratio is the secret.

Every single damm time, it's been the connecting rod big end bearing failing, but this was found to be caused by detonation from lean jetting in the standard NT carburettor used on the 80cc engines.

Once i went to a Dellorto No 84 main jet, all the problems disappeared, though the No 82 made the best power and the No 83 was the best combination between engine smoothness and power.
The No 84 makes similar power and the engine runs so much cooler and smoother.

Fabian

 

[thuginfc]

yea i agree i would much rather have a rich running engine than a lean one

my main jet was a problem with my motor at first it would be very jerky at low rpm but screamed power in mid-high range

i bored it out with an indexed bit set if i remember right it was like #70 brought it out to a 74 or 76 cant really remember the exact but thats where it ran smooth through all rpms

i can go wide open from a stop and it just seems to keep pulling until i gotta let off of it

also alot of problems come with the cheap chain and rag joint..finally got it really really close to true but i know in a week it will be thrown off again..time for a grubee hd wheel or a manic adapter

does matching the intake gasket/tube to the portmake that big of difference? i havent pulled this motor apart yet but my old motor the gasket kinda blew open so it was closer to port size. it would probably be a good idea to just get the manic intake when i order a new wheel/hub?