Running China Motor backwards ?? Successfully ??

[BigBlue]

Here' some information on timing from Grubee that might help:
http://www.grubeeinc.com/USA/Magneto Mystery.html

Looks like stock timing is 15 degrees BTDC.

Since you are now reversing the engine in the same direction as loosening the 8mm shaft nut, you might want to think about using some Loctite once you get everything dialed in.

Here's a video demonstrating magneto play:
http://www.youtube.com/watch?v=FhvaNvT5NN4&list=UL8sKg6h9pDmw

Good Luck,

Chris
AKA: BigBlue

 

[ToyTruck]

Thanks for the info

When I posted up asking for help , I was hoping someone would have done it before and could have just shown me a pic and it would have been too easy LOL

All I ended up doing was removing the magneto and the woodruff key , then finding TDC working back to about 15 - 20 deg BTDC to find the position of the magneto when it fires for NORMAL engine rotation.

So then I moved the crank to the New 15 -20 deg BTDC for the new rotation and put the magneto on , remembering that the engine now spins the other way.

I am sure this makes sense to those who have messed with timing.

Long story short I got it running , did half a dozen short test runs less than a minute. Did four 5 / 10 minute runs then when I was almost home ..... The motor locked up ..... Cooked the crank bearing on the magneto side ..... HAHA

New bearings ordered .....

This motor is the 4th kit I have bought and the only one to fail .....
I am going to assume it just failed and had nothing to do with reverse rotation ....

Will find out soon enough

 

[Deleted member 12676]

What kinda oil you using and at what ratio?
Something has to be way wrong to ruin that bearing.

 

[ToyTruck]

The oil is a Castrol synthetic race oil

Running the recommended run in mix.

Thinking back now , it had a squeal intermittently the whole time ...
I just put it down to clutch squeal ...
One of the times I heard it really bad , I had just done a 10 minute ride and because I didn't support my muffler , it cracked down both sides of the bend , I just assumed the squeak was the cracks as the muffler was shaking .

Everything else looks good , so I will replace the bearings and try again

 

[Fabian]

When the engine is running backwards the thrust is on the opposite side of the piston face. Considering pistons are cam ground, i'm not sure if this has an effect on the way the engine operates.

Does running the engine backwards require different port timing compared to an engine designed to run in the manufactures intended direction of rotation???

 

[ToyTruck]

The piston looks fine , no wear or damage ???

The motor is stock standard.
It was odd because , I adjusted the timing a couple times . And each time the seal popped out a bit behind the magneto .
I pushed it back so it was flush , set the timing correctly then started running it.

It's actually ironic , because the two previous kits that are running fine had real bad quality control ... This one looked perfect haha

I built my mount so if it is a bad way of installing , it won't take much to spin the motor round and add a jack shaft .

I appreciate the help with failure diagnosis , because I don't want to keep rebuilding after half a days riding !!
At this point I am going to get rid of my fuel and start from scratch with fresh 16:1 mix and just hope that it was a one off bad bearing.
I was lucky that it was barely running when it locked up

Fabian , do you really think port timing could affect anything ??

 

[ToyTruck]

I should add that I had oil dripping of all over the motor ....
I am sure it was not a fuel issue , but I want to rule it out.

 

[ToyTruck]

Here is a pic of my bike , plan is to raise the back of the tank and extend / lower the carby

 

[Deleted member 12676]

could be that the crank was wobbly which put extra stress on the bearing. Best to visually check it when its apart.
the odd location of the engine puts extra stress on the tire/wheel when hitting bumps. Also it puts additional weight on the rear which already has too much weight (since bicycles are incorrectly made that way). I would of mounted the engine closer to the shock.

 

[ToyTruck]

As far as the motor goes I am thinking it was either one of those things OR I possibly did some damage with it miss firing while I was getting the timing right .

Thanks for the suggestion to check the crank , I am tempted to do some porting mods while its apart .

As for the bike , as the rear suspension compresses , the seat and my back get very close to the engine , it does make it more unstable .....