Question about 1998 Honda CBR 250 RR
The bike was running fine but one day wouldn't start. Has been left sit for a couple of years and now decided to try getting it going. Have checked cam clearances, ok as per manual tried 3 sets of new plugs spark is very fine but a strong looking spark, motor spins over fine using big car battery. Spray Aerostart straight into carbs, will sometimes attempt to start but then it gives up. Will sometimes spit back through the carbs.Not sure if fuel pump is working but would expect the motor to fire for a second or two on the aerostart to give us an indication that spark/ compression and timing are all ok. I assume timing can't get out? What sort of compression should we be looking at. Manual says 40ps at so many thousand revs. What should I expect at crank over speed?
Any help or thoughts much appreciated
Guess I should post my answer as a solution so you can rate the solution. Clarifications can't be rated. Any results yet?
The timing should be okay. Sitting for two years will not change it. Pull all the plugs and give a shot of WD40 into each cylinder while pushing the starter button. This will get some lubrication to the cylinder walls and piston rings. It will also help the rings to seal up. Now do the compression check. The readings should be within 10 psi of the top reading. If using aerostart, spray it into the air cleaner not the carbs. The air cleaner will greatly lessen the chances of a fire caused by an engine backfire. Always have a fire extinguisher on hand when messing with the carbs.
Bear in mind that some of the rings may be stuck in the piston grooves and will not be free to spring outward to seal against the cylinder wall. The WD40 may help here also. The worst case is that you will need to pull the head and cylinder to physically free the rings. Your pike is now 19 years old and the valves have probably never been worked on. Now would be the time to re-seat the valves. Depending on the condition of the cylinder, piston and rings, you may want to re-bore the cylinder and mount new piston and rings. At least run a cylinder hone through each cylinder.
I was going to just post this as a "clarification" but have sort of gotten into it now. All I ask is a "Helpfull" rating The "Thanks for trying" rating is a real bummer for a guy just trying to help. Get back to me.
Not sure what manual you have but compression is never checked at anything above idle. Crank and idle speed compression should be 140 to 160 psi.
Posted on Jun 03, 2009
Its alot of work clean your carbratuur fully. ill think your starter jets are closed. if fuel dry out it a glue. greeds j kerkhof
Posted on Aug 02, 2009
Bikes are kind off funny that way... i mean after sitting for so long, the piston rings will sometimes colapse and you get low compression carbs prob need cleaning. but you can try this. take the air filter off and hook up a good strong battery, a jump from a car or truck running is best. with "NO" choke, give it full throttle and spray starting fluid directly into the carbs while hitting the starter button.. hope this does it for you.
Posted on May 31, 2009
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Posted on Jan 02, 2017
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