Engine Trouble Let the Clutch out andthe wheel locks !!!

[Icefire]

Hope someone can help me out here. I have installed 4 Grubee 66cc engines or the past 3 years and have have no issues running them and ended up selling them over time. I picked up an 80cc ??? from toys for Boys about 3 weeks ago. Had it running and was able to put 4 plus hrs run time on er. Then I went to start it the next day and when I let the clutch out you could hear it sliding but the engine would not engage. After adjusting the clutch a few times it would either slide with engine not engaging or if I adjusted it a bit more and let the clutch out the back wheel would lock and the engine would not turn over, go figure. I took the clutch assembly out and was able to turn the crank gear freely although there was a bit of resistance at certain points but nothing too bad. I put the clutch assembly back together and when the clutch lever is squeezed the bike will roll freely, once the clutch is let go the back wheel locks and the engine will not turn at all.
Has anyone here come across this type of issue with their ride? My grubee is still running strong but cannot understand what is causing this unknown brand to not turn the engine over anymore?

 

[crassius]

lock the clutch so the back wheel turns freely, take out the spark plug, open the magneto cover and try to turn the rotor to see if the motor is seized

 

[Icefire]

Ok, looks like the crank shaft is binding at certain points as I have to use a socket to turn the magneto when the clutch is locked out. I removed the motor from the bike today and have taken the side covers, cylinder, crank gear, clutch assembly and magneto. Will get
On splitting the cases tomorrow and check to see if the bearings are causing the binding .

 

[Icefire]

I was able to get the cases split today and once I pulled the crank I found the problem. The ???? Split into 3 prices causing the crank to seize which in turn caused the back wheel to lock when releasing the clutch. No idea why his would happen and does nyone know what this part is called?

 

[Big Red]

They use this to balance the crankshaft. I had one come loose before, jammed the engine, but it stayed in one peice. My only suggestion is to see if ya got one on an old motor that will fit cause now that you took it apart ya can't send it back. I've never seen one for sale all by itself. I probably have a few in my shop on an old motor if you don't have one. I'm not sure it would work though. I think they balance it to each motor.
Big Red.

 

[HeadSmess]

this is why, firstly, i really will never bother with an 80, breaking balance weights? if youd been doing 8 grand at the time...o boy!


nope. stick to what you know and trust and dont go believing that bigger is better. its always the one odd one that you buy that will give you the screamin raging


but, as for the weights themselves... there appears to be no difference between the 48 and 66's, but then, i havent pulled them off to check the holes drilled in them. so i dare say they 66 and the 80 will also be the same.

as long as the diameters are the same, it should be fairly easy to drill the odd hole in the correct spot to get the balance back ... just a larger amount of material kept to counter the extra piston weight of the larger engine, etc...

 

[Big Red]

49cc or 66cc, They are all put together by the same quality control "engineers". The difference may only be that the 49 doesn't have enough power to throw a weight off.
And ice, like I said, If ya don't have an extra weight let me know and I'll mail ya one. That is if you think you can balance it. Otherwise yer lookin at buying a new crank.
But I got no beef with the 49cc crowd. If thats what you prefer then go with it bro. Like I've always said,
IT'S YOUR BIKE, BUILD IT YOUR WAY.
Big Red.

 

[HeadSmess]

im just prejudiced

my money on why it happened? bad luck and chinese steel... capacity has nothing to do with it

its definitely a first from what ive seen seen rods crack and other fancy things but for a weight to break? oh my. shelf item. trophy number 1!

 

[Big Red]

I've had two come loose over the years. Neither one busted up like that.
Yeah, I was just funnin with ya bro, A weight coming loose has nothin to do with the CC's. Just another example of Chinese quality control at it's best.
Big Red.

 

[Icefire]

Well after checking around they do not sell the weights separately, you have to purchase the complete crank assembly to get the weights. So I have ordered a new 66 cc Grubee which I trust more and have shelved the left over parts from the black no name. Should be in this week.