Posts
143
Joined
8/2/2018
Location
Chandler, TX
US
I need help. I have a 250f that doesn't want to fire up. Looking for help on what the compression should be on these new bikes. I haven't checked compression since the 2 stroke era. Is there any special procedures with an electric start? I appreciateal any help on this.. .
How many hrs on it? Does the fuel pump come on when you hit start button?
The bike has 40 hours. As far i can tell so far the pump primes when you hit the button. All the fuel lines are clear and there is fuel in the line after you try and start it. I checked the fuse on the starter relay and still nothing.
Remove the air filter and spray starting fluid in the intake as you crank it to see if it fires. If it fires on starting fluid you have at least narrowed it down to a fuel delivery issue. If that doesn't work, check spark next.
Its got spark, i an pretty sure its getting fuel. That is what leads me to believe its down on compression for whatever reason. The motor seems a bit "free" when turning over. I am just not sure what the compression number should be for a moden four stroke with electric start.
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Free shipping: VITALMX
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Leak down test is much more valuable than a compression test on a thumper. If you have compression issues this will also reveal where (intake valves, exhaust valves, or rings).
Unfortunately i dont have the tools necessary for a leak down test. A compression test is more to figure out if i should pull the motor or keep chasing electric issues.
I have heard the compression test won't tell you much if there is an auto decompressor on the engine, which all modern 4 stroke race bikes have.
Exactly, i dont think its going to have thebsane benefit as a 2 stroke test but i believe there is still a range of acceptance. I am just not sure what that range is.
Need to do the Leak down
Hello! Did you solve this issue? Im having the exact symptoms in my Husqvarna FC250 24, it doesnt want to fire up, the gas pump seems to prime, my mechanic made a compression test and turned to be 50psi which he told me was too low, that the valves might be to tight
The 23's 250's are notorious for catching a ring. I have seen it more than once now. Fortunately most just need a piston and ring and everything is good to go after that.
So you had to change the piston and rings? it was stuck? Im not sure that is my huskys problem then, because I was able to turn it on by pushing it down a hill, when it is hot it turns on easily, but when the engine got cold it wouldn't start again
pretty weird, its a '24 with only 74 hours on it. The day before everything started I made quite a long trip, could it be possible that because of this the engine overheated and the valves got too tight?
The symptoms you describe (hard to start when cold but will push-start and easier to start when hot) are the most common traits of tight valve clearance. If you keep riding it with tightening valves, eventually it will get hard to start even when hot.
Post a reply to: 23 KTM 250 SXF Compression Test