I changed the piston rings on all 4 cylinders because the compression was so low and the bike would not start, hooked back everything together tried to start it and heard a big bang, backfire from the exhaust...I won't start...I got Fuel and the plugs seem fine, new float valves in the carbs, the carbs are clean too...When I pulled my plugs out after attempting to start the bike they are wet...Seems the spark is not powerful enough to ignite the air/fuel mixture...but I double checked and there IS a spark from all 4 plugs....


Help me guys I'm going crazy...

 

A motor requires three things to start, fuel/air mixture, spark, and compression. If you are posative you have spark, and fuel, then you must be missing compression or your timing is sooo far off it wont fire at the right time to ignite. If your plugs are wet it would seem to me that there isnt any spark going on, I can only assume you put the plug on something and turned the motor over to witness the spark? If you did infact see the spark, your timing seems to be 180 off which will cause the same symptoms.

 

I just changed the rings, all new, I doubt it's the compression, and the timing was done perfectly while reassembling the engine...I see spark when I ground a plug to the motor but is there a good spark once the plug is in the combustion chamber...I have no idea...I'm running out of ideas and patience, i've been working on this bike since the month of may...

Any inputs are greatly appreciated...

I got compression, spark and fuel...

A good strong spark, i don't know...

 

The big bang/backfire sounds like maybe you reversed the plug wires or the feed wires to the coils when you put it back together??? Not that I have any personal experience that tells me that.... nope NEVER done that myself! [:@]

 

I double checked and the plug wires were in the right cylinder and the coils were wired right...
I checked the resistance in the primary and secondary coils and they are in good range...

Keep em coming I want to start this bike!

 

I'm NOT a mechanic but that big bang still makes me think the plugs aren't firing at the right time. If the coils and wires are hooked up right... could the cam timing be way off?

 

Bottom line is you need some new plugs. Once they get wet like that they are junk.The bang is the gas building up for a cyclinder or two (which was not firing because the plug was fouled) in the exhaust and finally igniting. I highly doubt anything is wrong with your timing. Your compression is fine so dont worry about that. Maybe new plugs will fix your problem... if they foul out again you have to look into why they are fouling out. Try that and let me know. Believe me its not as bad as you think.

 

I don't understand this...The plugs were brand spanking new..cranked it once, 2-3 seconds and boom, backfire...So now my plugs are toast? A set of plugs is 50$...I am not made out of money I can't go buy 3 dozens of plugs and changed em each time the bike backfires till it starts...So why could they be fouling????


Thanks guys...

Dominic

 

Pff I just wipe off fouled plugs and chuck em back in. Never had a problem.

 

It has nothing to do with plugs. I think you installed one of your camshafts 180 degrees out. I've seen it happn before. Go back and double check with the manual that you have everything installed correctly.