Help FZR 250 not starting

1 cylinder not firing shouldn't stop it from starting. It should start on the other 3. I think your problem may be more than that... but here's hoping all that digging fixes the issue

 

Valve clearance being out is but one cause of a cold cylinder. Could be a dead plug, dodgy coil lead, or something else entirely.

To rotate the engine when checking valve clearances, take off the stator cover and rotate clockwise when facing the stator. You will see the timing mark on the stator and the arrow on the crankcase. That will be top dead centre for cylinder 1 or 4 (check against the timing marks on the camshafts, which are on the left side of the bike.) You will notice that the intake and exhaust cams will be pointing opposite eachother, eg intake lobe will be pointing to the carbs and the exhaust lobe will point out above the exhaust port. That is when you measure the clearance for each cylinder.

There should be some amount of 'drag' on the clearance, so don't be alarmed if it is slightly stiff, but you shouldn't be struggling to get the feeler gauge in.

Speaking of feeler gauges, they won't come with the exact clearance spec needed for this bike, but they will be close enough (eg, if the 0.127mm gauge doesn't fit under an intake, but the 0.90mm once does, assume the valve is not within spec and replace the shim).

Shims will be numbered, eg 150, 162. That is the thickness on the shim in mils. Numbers should go face down when replacing shims, and should be lubed with moly grease. If you by a shim kit, generally they will only come in 0.05mm increments. In the case that you measure and need a 162 and you only have a 160 or 165, use a 165. More clearance is better, as long as it is within the spec.

You can also swap shims around to different valves, this can save you if your shim kit doesn't have enough of 1 size.

Attached is a zip file with an excel spreadsheet you can use to record your measurements, and the size of each shim that's installed if you intend to set the clearances. The clearance specs for the FZR250 are in there too.

 

No problem!

If you need shims try precisionshims.com.au

Otherwise if you're really desperate I have a hot cams shim kit, let me know what you need and you can send me your leftover shims.

You will have to remove the cam chain tensioner and camshafts to get at the shims though, there are threads that can help with that

http://2fiftycc.com/index.php?threads/fzr250-cam-chain-tensioner.3336/
http://2fiftycc.com/index.php?threads/fzr250r-how-to-change-your-cam-chain-w-o-splitting-cases.3456/

 

Absolutely, all the valves are out of spec. Doing a compression test at this stage would reveal below spec compression, but no need to do it now. After would be a good idea to get an idea of the condition of the rings

You will need to record the thickness of each shim to figure out what new shims you can swap around and how many you need to order.

 

Dad's FZR was dropping a cylinder on the highway and required full throttle to maintain speed until it came good again. Then it stopped running entirely and I couldn't keep it going even with a roll start and full throttle. Cylinder 3 was stone cold. As with yours, all the intake valves were too tight except for one, which was on the too loose side of the spec. Exhaust valves were tight as well. Runs like a top after doing the clearances.

We also did the needles and tubes at an earlier date.

 

Yes they are.

 

So I'm a little confused.

Ok so what did you originally mean by "has compression"? was the compression even in spec to begin with?

Mine runs without air filter as well, but noisily. Could be a contributer to your "bad running", it is also harder to start without it but only marginally.

Did you mean "won't start" instead of "won't turn over"? They're different things...

A contributing reason perhaps. You may have crossed a low compression threshold that prevents it starting from the key, but I'd think spinning the motor fast enough through a push start may still get it going.

They are out by a fair bit so low compression seems to be an issue. Fixing it may or may not fully resolve what you are seeing but here's hoping it at least gets the bike started again. I have a bunch of 7.48mm shims so let me know what sizes you need and I may be able to send you some cheap if I have the right size. Precision shims is the alternative, but given the number you need it adds up quickly ($5.50 per shim plus postage I think).

My FZR ran with all the intake clearances out and one exhaust out. It had a ticking sound but I wouldn't say it ran "badly", just "noisily". If your pilot hole is blocked you'll have immense trouble starting the bike so if you have the carbs off I'd be looking at that one very closely. Here's an example: http://www.2fiftycc.com/index.php?threads/stus-fizzer.3200/page-11#post-41815

Good luck