Custom/Hybrid BOB backfire

[ChrisFiore15]

Whats the date on that MSD?

 

[stg5685]

Whats the date on that MSD?

its scratched but it looks like 1990 something hopefully atlantic jetsports gets my new one here by the weekend

 

[KTM434]

FYI the new enhancer comes with installation instructions and wiring diagram too

 

[stg5685]

FYI the new enhancer comes with installation instructions and wiring diagram too

thanks it would be nice if this fixed it if not looks like ill have a msd for sale.

 

[KTM434]

thanks it would be nice if this fixed it if not looks like ill have a msd for sale.

Let me know if you get frustrated enough that you end up having a BOB for sale

 

[customride0105]

I'm noticed the marks on the nose of the crank. Check the flywheel for a crack and keyway is good on the flywheel.
What carbs? Am ? If so did u remember to put a jet back in the return fuel line?

 

[Proformance1]

FYI, not that it should matter for you but the MSD instructions are incorrect on the battery and starter lines. They are swapped on the sketch. Im still sticking with my orig statement of places to look but next would be a stock known working CDI from a running ski.

 

[stg5685]

I'm noticed the marks on the nose of the crank. Check the flywheel for a crack and keyway is good on the flywheel.
What carbs? Am ? If so did u remember to put a jet back in the return fuel line?

i havnt pulled the carbs since i bought the ski when i did the swap i left them on. all i did was replace the fuel line. they are mikuni 44s

 

[customride0105]

Are they novis full spec modded carbs most drill out the restrictor. So fuel has no back pressure and will cause backfires. And u said u replaced the fuel line my bet was there was a jet in the line and u didnt notice it.

 

[stg5685]

Are they novis full spec modded carbs most drill out the restrictor. So fuel has no back pressure and will cause backfires. And u said u replaced the fuel line my bet was there was a jet in the line and u didnt notice it.

replaced the lines after it was back firing as an attempt to fix it

 

[Proformance1]

Are you just trailer running or water testing and saying that its still backfiring? Residual fuel in the exh will cause this, you must get the pipe hot and burn it out.

 

[KTM434]

Maybe I'm wrong but I thought it was backfiring and wouldn't even start. That would make it hard to burn the fuel out of the pipe

 

[Matt_E]

Are they novis full spec modded carbs most drill out the restrictor. So fuel has no back pressure and will cause backfires. And u said u replaced the fuel line my bet was there was a jet in the line and u didnt notice it.

How is low fuel pressure going to cause backfires?

 

[stg5685]

Maybe I'm wrong but I thought it was backfiring and wouldn't even start. That would make it hard to burn the fuel out of the pipe

you are right it cranks, i get spark , i pull fuel but never turns over and when i let off the start button it backfires

 

[Matt_E]

Turning over = engine cranks.

You mean it doesn't fire up?

 

[tomski]

you are right it cranks, i get spark , i pull fuel but never turns over and when i let off the start button it backfires

ok so before i order a new msd how do i check the woodruff key? it is a violent backfire and its as soon as i left off the start button. Another question can you have a bad msd enhancer and still be getting spark?

Enhancer

 

[stg5685]

Turning over = engine cranks.

You mean it doesn't fire up?

you are correct

 

[rubbertoe]

have you tried priming it before you start your motor ? just a thought.

 

[KTM434]

Turning over = engine cranks.

You mean it doesn't fire up?

You're welcome! You have 500 thank you's now :headbang:

 

[Blue]

I had a msd enhanser go bad in berkys freak it did the same thing. swap it out i bet its bad. Try a stock cdi just to test.