I posted a while back about my blaster missing out at full throttle and am just now getting to checking it out. It runs fine until I really get into it and it starts missing out till I back down then its ok. I jacked it up, put on a spark plug tester that has a light and ran it. When it started missing out I still had spark. So, it must be jetting, or fuel issue? I thought I had it jetted ok after my rebuild last spring, but maybe not. Also, i've noticed its gradually getting harder to start cold, once its hot starts first kick. Compression-after 3-4 kicks is 95 steady, so I know its low. Maybe rings didn't seat right. So could maybe it not been getting enough fuel, then got to hot and maybe I need new rings now? Last spring I rebuilt bottom end with all new bearings, gaskets, seals, new piston & rings, and bored out to .5. It has fmf pipe with pro circuit silencer, k &n filter, air box lid on, tors removed, oil injection removed and pre mixing 32:1 with PJ 1 goldfire pro 2-stroke oil. Stock carb with main jet 280. I am in kansas at 3000 ft. I will get leak down test done tomorrow night. Any thing else I need to look for?
Still missing out, ready to get this fixed!
- Thread starter quepasa69
- Start date
Might need to bump that main at 3000ft. Try a 290 or 300.
Tried a new plug? Fresh fuel? Cleaned the carbs? all the basic stuff?
You definitely need a bore and hone with that low of compression. Dont forget to wash out your freshly bored cylinder with a rag and some dish soap. If you dont clean out all the old metal shavings itll fry your new top end. That is also why its getting harder to start, low compression... It wont run anything less then 90ish
Tried a new plug? Fresh fuel? Cleaned the carbs? all the basic stuff?
You definitely need a bore and hone with that low of compression. Dont forget to wash out your freshly bored cylinder with a rag and some dish soap. If you dont clean out all the old metal shavings itll fry your new top end. That is also why its getting harder to start, low compression... It wont run anything less then 90ish
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Yes new plug, new fuel, cleaned the carb, blew all ports out still same problem. Would I have to bore it out again, could just the rings be replaced? Guess it depends when I get it apart and what it measures? Do you think the small jet caused the problem?
The jet definitely coulda caused the problem. I would need to see the inside of the cylinder to see if it needs a bore... You can put a fresh ring in there if you have one and measure the ring gap to see if you need a bore and hone. Usually you do if you lose compression....
You would have to check plug to know if its rich or lean. Usually higher elevation is leaner. Also depends highly on airbox lid being on or off and yours is on. I would try removing it.. Do another compression test and kick it over like 10 times or until the tester stops increasing.
Simple test to see if your rings are fried is to do a compression test after that test squirt a little premix down the spark plug hole and then retest the compression.If you have a jump in compression with the oil in the cylinder thats because its sealing where the rings arent and a good indication of ring issues.
95 psi says to me that there is a ring problem. Put a 300 main in and see if the miss problem goes away.
With that low compression you most likely will need a new set of rings and maybe a piston if the condition was caused by too lean a mix.
When you pull the head off the state of the piston crown should tell you what caused the problem.
With that low compression you most likely will need a new set of rings and maybe a piston if the condition was caused by too lean a mix.
When you pull the head off the state of the piston crown should tell you what caused the problem.
well thanks guys! Im going to try the bigger main and see if that will help with the missing out, and I will try what you all said about checking the compression some more. Im going to wait till the end of the month after I go to a poker run and then I will pull the top end apart as I will be done riding for a while. Hope I don't have to bore it again, the nearest guy that does them charged me $90....and maybe it wasn't bored properly last time.
A leaky head gasket can act like jetting issues at higher rpm. other than that sputtering at high rpm is indication of too rich. make sure the air cleaner is clean also. a dirty filter will cause a rich scenario.95 psi is dangerously low! i would do a leak down test.
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