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Fuel, spark, compression - no start
Posted: Thu Nov 27, 2025 3:49 pm
by Rideslikenacho
Ive got a no start condition and out of ideas on this one. Has fuel, spark, and 145 compression on new top end.
Done the following:
New plug(s)
Added oil to the cylinder after new top end
Replaced crank seals
Replaced carb with new
New cdi & ignition coil for original no spark condition
Fresh gas
Fresh oil
New gas lines, petcock, and fuel filter
Reeds are good and sealing
New air filter and air box top held on correctly with no holes
Won’t even pop with premix added to spark plug hole. Which tells me it’s possibly not getting spark. That said, turning it over with plug held against frame its definitely getting spark. Also tried starter fluid once just to see and nothing. Removed the exhaust and same thing so not clogged exhaust, but getting fuel out the exhaust hole so carbs letting fuel through. I’ve ordered new plugs to try and see if thats the issue.
The bike ran after the top end rebuild, began heat cycling it but only rode it a very short distance down the road and put it away for the day. Came back and had issues above for no reason.
Any ideas?
Re: Fuel, spark, compression - no start
Posted: Wed Dec 03, 2025 12:42 pm
by mousewheels
Won’t even pop with premix added to spark plug hole. Which tells me it’s possibly not getting spark. That said, turning it over with plug held against frame its definitely getting spark.
Do you get a spark with the plug grounded to the head/engine rather than frame?
Re: Fuel, spark, compression - no start
Posted: Wed Dec 03, 2025 1:55 pm
by Rideslikenacho
mousewheels wrote: Wed Dec 03, 2025 12:42 pm
Won’t even pop with premix added to spark plug hole. Which tells me it’s possibly not getting spark. That said, turning it over with plug held against frame its definitely getting spark.
Do you get a spark with the plug grounded to the head/engine rather than frame?
Yes definitely good consistent spark when grounded to the frame.
Only change I can account for after it ran is I added the rear turn signals thinking I had the engine stuff complete. So maybe a ground issue or something. I need to check that next.
Re: Fuel, spark, compression - no start
Posted: Wed Dec 03, 2025 8:44 pm
by bonesv
Rideslikenacho wrote: Thu Nov 27, 2025 3:49 pm
Ive got a no start condition and out of ideas on this one. Has fuel, spark, and 145 compression on new top end.
Done the following:
New plug(s)
Added oil to the cylinder after new top end
Replaced crank seals
Replaced carb with new
New cdi & ignition coil for original no spark condition
Fresh gas
Fresh oil
New gas lines, petcock, and fuel filter
Reeds are good and sealing
New air filter and air box top held on correctly with no holes
Won’t even pop with premix added to spark plug hole. Which tells me it’s possibly not getting spark. That said, turning it over with plug held against frame its definitely getting spark. Also tried starter fluid once just to see and nothing. Removed the exhaust and same thing so not clogged exhaust, but getting fuel out the exhaust hole so carbs letting fuel through. I’ve ordered new plugs to try and see if thats the issue.
The bike ran after the top end rebuild, began heat cycling it but only rode it a very short distance down the road and put it away for the day. Came back and had issues above for no reason.
Any ideas?
Yea, I have an idea. Look at what happened when you rode it maybe? Check the compression again. It takes a good while to seat rings. It needed more heat cycles and let cool off completely. Use a fan and leave it until it is cold.
Riding it is not heat cycles. Let engine run without fan shrouds on it.
USE A TEMP GAUGE ALL THE TIME! Also, the carburetor, where did you get it from? eBay?

Clean the old one and use it instead. Do the tuning patiently or it will be unhappy just like you will.
Re: Fuel, spark, compression - no start
Posted: Wed Dec 03, 2025 10:32 pm
by Rideslikenacho
Yeah so I heat cycled it like ten times while letting it cool completely between each, then rode it up the street and back. I probably should start putting a trail temp on them after a top end rebuild. Carb is cheap amazon one which I still do wonder what that extra nipple is coming off the engine side, always assumed it was vacuum line and have them capped off on my other Sprees.
Re: Fuel, spark, compression - no start
Posted: Thu Dec 04, 2025 6:25 am
by bonesv
Easy fix is if the temp is above 380 then you upjet AND check for any air leaks into motor. The high temp represents a lean condition and you have to remedy it. It's not hard to find the problem.
Re: Fuel, spark, compression - no start
Posted: Fri Dec 05, 2025 6:23 pm
by Rideslikenacho
bonesv wrote: Thu Dec 04, 2025 6:25 am
Easy fix is if the temp is above 380 then you upjet AND check for any air leaks into motor. The high temp represents a lean condition and you have to remedy it. It's not hard to find the problem.
Yeah if it was running, problem not is getting it to turn over. 95% sure its something to do with a ground since rear turn signals were not on when it fired up after the rebuild. Once I get some time and weather cooperates will try that.