Complete Engine rebuild- NOW NOT RUNNING- I Am lost

[Blasterbuilder]

Hi guys i just got the motor together on my project blaster and it does not want to run. it occasionally backfires, and just doesnt want to start. It has a keihin carb and VF3 reeds. I rebuilt the top and bottom ends of the motor. Even when i pull start it behind another wheeler it doesnt want to stay running or even really go.

It has good compression,spark, no leaks, and have cleaned the carb 4-5 times. should i go back to stock carb/reeds or?????

let me know, tx

 

[Blaaster]

Put back the carb it was running on before rebuild, the new carb may be jetted wrongly.

Could the flywheel have spun shearing the timing key?

 

[blasterdemon7]

What was the compression reading? How long did it hold at 7psi on the leak tester ? Do you have spark?

 

[Blasterbuilder]

What was the compression reading? How long did it hold at 7psi on the leak tester ? Do you have spark?

Compression is 120lbs, i have always used leak soap on my blasters and its always worked, spark is also good.

Are keihin carbs just touchy and worthy of getting rid of??

 

[Blasterbuilder]

Put back the carb it was running on before rebuild, the new carb may be jetted wrongly.

Could the flywheel have spun shearing the timing key?

The keihin carb was on before, and good idea ill check flywheel right now..

 

[blasterdemon7]

Also check you reeds good for gaps, cracks or chips.

 

[Blasterbuilder]

Alright guys blaaster was right it was a sheared flywheel key, so ill get one of those and get rippin again, thanks for the help guys

 

[Blaaster]

Compression is 120lbs, i have always used leak soap on my blasters and its always worked, spark is also good.

Are keihin carbs just touchy and worthy of getting rid of??

Whats leak soap?

Is it soap that stops leaks?

Did the leak test hold 7psi for 10 minutes?

 

[Blaaster]

Alright guys blaaster was right it was a sheared flywheel key, so ill get one of those and get rippin again, thanks for the help guys

If that flywheel has spun, you may need to inspect it to see if it needs lapping.

If there any marks or scores on the taper, chances are that it will, sometime in the future, spin again.

It is not the key that stops it spinning, but by tensioning up the interference fit between the shaft and flywheel tapers.

 

[Blasterbuilder]

If that flywheel has spun, you may need to inspect it to see if it needs lapping.

If there any marks or scores on the taper, chances are that it will, sometime in the future, spin again.

It is not the key that stops it spinning, but by tensioning up the interference fit between the shaft and flywheel tapers.

What does lapping the flywheel mean?

Whats leak soap?

Is it soap that stops leaks?

Did the leak test hold 7psi for 10 minutes?

I should rephrase: leak detecting soap that makes bubbles when a leak is present

 

[Blaaster]

Lapping the flywheel consists of putting some fine valve grinding paste on the taper of the crankshaft, placing the flywheel on, ( without the key), and revolving the flywheel back and forth.

When the flywheel turns more freely as the paste gets broken up, take off the flywheel, wipe out the used paste and inspect.

The grooves should now be flattened out.

If there are still grooves, repeat the operation until good mating surfaces are made.

Be sure to wash off all, and I mean all of the grinding paste.

I like to finalise by using a Duco cutting compound No 3 for the final lap.

Tension the nut to 53 ft lbs, some use Loctite but I never do, it is not the nut that holds it on, it is the pressure applied to the tapers.

 

[blasterdemon7]

Alright guys blaaster was right it was a sheared flywheel key, so ill get one of those and get rippin again, thanks for the help guys

Glad you found the problem and it was an easy fix.