357xp backfiring after rebuild but won't run

[matthewkent2504]

So I have rebuilt a 357xpg  it been a on going project for some time. 

 

It has good compression but on trying to start it it backfires. 

 

Could this be due to a 357xp flywheel being used not the 357xpg 

 

It clearly a timing issue but am at a lose. 

 

Am wondering as the first flywheel sheared as I forgot to tighten it down enough. 

 

Or is it the Coil as it got the coil from a 357xpg and it now a 357xp 🤔

 

Thanks for any hlep 

 

Matt 

[Stubby]

1 hour ago, matthewkent2504 said:

So I have rebuilt a 357xpg  it been a on going project for some time. 

 

It has good compression but on trying to start it it backfires. 

 

Could this be due to a 357xp flywheel being used not the 357xpg 

 

It clearly a timing issue but am at a lose. 

 

Am wondering as the first flywheel sheared as I forgot to tighten it down enough. 

 

Or is it the Coil as it got the coil from a 357xpg and it now a 357xp 🤔

 

Thanks for any hlep 

 

Matt 

I think you have said it . Possible sheared flywheel key is my first thought .

[adw]

No problem fitting a non g flywheel, so as been said you may have sheared the flywheel key again, when you say rebuild what other parts have you fitted?

[spudulike]

The XPG and XP are the same metalwork but the "G"has a circular magnet bonded to the back of the flywheel.

As others have said, the most common cause will be a sheared flywheel key. A really dodgy Chinese coil gone bad may cause backfiring but less likely.

How are you doing up the flywheel? A piston stop and torque wrench may be best. I suspect a rattle gun!