My 450 sx just quit running last winter.Noticed a loss of compression.After looking at the bike I noticed that when I kick it over the bike is sucking air through the exhaust and pushing air out of the carb.I am mechanically inclined but i dont really know what to do fix it.Any reply would help thanx. First badass dirtbike i have ever owned looking to get it fixed.
Hi , This sounds suspiciously like a valv problem. Maybe a valve got bent and is stuck open. If you are mechanicly inclined , are you up to the job of removing the rocker cover for a look?? If you are do this and with the spark plug removed turn the engine over and see what the valves etc are doing. Also worth checking is , your cam chain is ok, valve timing.
Is there any binding when the piston reaches TDC. Is it maybe hitting a valve?
If you are not sure about this stuff tho. Take it to a shop.
Hope this helps.
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some bikes will let you start with the stand down, as long as the clutch is in, same with it in gear.
some bikes wont let it start at all in gear, or with the stand down.
All suzukis usually work the same.
hi,this should be fitted with a decompessor,if it is not,then try this,gently turn the bike over with the kicksart untill you feel the piston coming up to top dead centre (you will feel the compression rising)thenlet the kickstart return to its normall position,now give the kickstart a good healthy kick and the bike should fire up,if you think a 450 is hard work,wait till you try a 500 velocette with no decompessor if you dont get those things right they will either fire you over the handle bars into the workshop bench or break your leg in the process or worse a combination of both the above..good luck..hope this helps...cheers
Yes, it does have an automatic decompression mechanism. It is a centrifugally operated mechanism and it is EXTREMELY unlikely that is causing your problems. The two highest probabilities are: 1. Fouled spark plug. Forget what it looks like, put a BRAND NEW plug in. It is the cheapest form of diagnosis you can do. These bikes are terrible about fouling spark plugs and a fouled plug produces the exact symptoms you described. 2. Inspect your valve clearance. Tight valves will also make the bike hard/impossible to start with the kick starter. In some cases, it can be push started, but still won't kick. With tight valves, the bike, although hard starting, will run pretty good, for awhile. Eventually it will burn the valves and quit running though. If your bike isn't kick starting fairly easily, something is wrong and needs to be addressed. The only other issue is making sure the idle speed is set per the service manual. These bikes have a fairly high idle, some as high as 1700 rpms. If it is set too low, it makes them hard to start too.
the bike might have to much oil in the bike so when you try to kickstart it, it sends oil to the piston and soaks the spark plug in oil. But when you push start it the spark plug is going alot so it catches, just kicking it doesnt give enough spark tho. my bike doesnt the same and then somtimes i have to take the spark plug out and clean it with a wire brush then usually its fine. Or you could have the wrong oil in the bike, i would read the maunal to find the perfered oil. hope this helps
Oil from the breather is an indicator of compression bypassing the rings. This causes sump compression.
Cause of the problem is worn rings.
You need to conduct a compression test, if the compression is low then rings are probably the cause of the bike not starting.
I also had a bike rebuilt on the top end, which also poped when kick starting. I thought it was going to start, but never did. I used a compression tester gauge on it and found that I had 60psi instead of 100psi. I had it rebored buy a different shop and they informed me that the last shops equipment bored the cylinder oblong instead of cylindrical.
I was out the money from the first shop but I did get it fixed. Hope this helps
You need to inspect the valve clearances. It is common for the intake valves to wear a little.
Inspection of the clearances should take place at 15 hour intervals if you are racing the bike.
When the valves leak, the bike does not maintain compression and kick starting becomes tough. The fact that the bike starts when being bumped, shows a loss of compression.
An easy DIY compression test is to remove the spark plug, place a finger over the plug hole and press down on the kick start lever. The air should be forced past your finger at a high rate and you should hear the air escapeing. You must not be able to prevent any air from escaping.