Help FZR rough idle

Carb sync is the last step of the job. Start with valve clearances, spark plugs/leads, set pilot mixtures to 3 turns out, clean or replace the air filter and then do carby sync.

Check the carb & airbox boots on the fizzers as they go hard and shrink with age.

 

You need to do your valve clearances

 

As motors wear, the clearance between the valves and the camshafts decreases. This happens because the valve seats wear and the valves start receding into the cylinder head. Tight valves result in a hot running engine and possibility of burning out valves due to extreme temperatures. If there is no clearance at all then the camshaft is holding the valve slightly open and compression gasses are escpaing before they should - there's your low exhaust temperature explained

Doing clearances is pretty standard servicing. Any bike shop will do them, but expect to pay $120 an hour plus whatever parts are needed.So basically a valve cover gasket and up to 16 shims. It's a good idea to replace all the shims and get all the valves up to the maximum clearance spec, as it means you probably won't have to do them again for a very long time. Plus, you have to remove the camshafts to change the shims.

Unless you have the space, time and tools to do the job yourself, I'd be getting a bike shop to do it.

 

As Linkin said - valve clearances, when out of spec, mess with your cylinder's ability operate correctly. It is much more frequent in the service schedule than a carb sync, and will have a bigger impact. I'd bet your clearances on cylinder #1 are out.

It's not hard to do, it's only expensive because it's time consuming. Measure it correctly and a new shim is like $5 each. I even have a baggie of spares i could hook you up with (if I have the right sizes).

We can talk you through it, I need to put my other FZR engine back together anyway so maybe I'll do a video or something. Also, read/watch some things eg this video I did:



to teach you some basics. It's how we all learn

 

Easier to do it at home. Only need basic tools - feeler gauges, torque wrench that does 10nm, socket/spanner set, veriner calipers or micrometer will get you through it. Oh, and this sheet to record your measurements: https://2fiftycc.com/index.php?resources/valve-clearance-sheet.232/

Your typical FZR250 will probably need all 16 shims changed out, keeping in mind you can swap shims around different cylinders to minimise the amount of new shims you have to buy. As well as a new valve cover gasket. Part number 1HX-11193-00 - Yamaha dealer should be able to get them, tell them its for a Zeal - some places will kick up a stick about grey import bikes.

This thread will help you a lot: https://2fiftycc.com/index.php?thre...ange-your-cam-chain-w-o-splitting-cases.3456/

Clearances should be measured when the cylinder is on top dead centre of the compression stroke, with all the valves closed. The camshaft lobes will be pointing away from the valves like so:

 

best thing to do first is a new plug. plugs can give funny problems. had that on a cb350 and non contact infra red thermometer picked it up.after that the mixture screw but check choke is off. then valve clearances. hopefully you will not need that stage. could also be faulty plug lead or cap. start with simplest/

 

Your header temps are low, but fairly consistent. They should be up around 240c-250c. That plug also looks very fouled. I'd be replacing all four plugs and looking at the condition of your air filter next.