drewpy

UK bikes don't have relays. the 4th wire feeds the main beam pass switch. I had to solder an extra wire from the ignition switch live to the pass switch on the left side and back to the headlamp main beam.

its your pilot jet, this is the smallest drillings in the carbs and will clog up first. You also need to fit a fuel filter as your tank will have rust particles from gas stations and in the tank itself. Try some of the proprietry carb cleaner you put in the tank and see if it unblocks. You could also open the screw another 1/2 turn and see what happens. mine always runs the roughest at 4k revs. this is the point where the main jet starts to take over from the pilot system. Just age and 30 year old technology really.

If youv'e had the bike from brand new and you can say you have never had a screw driver on the pilot, you can eliminate that then. if you have the carbs off, take out the pilot screw and feel under neath for a little "pin" if its there its snapped off!! Its an air screw, in for rich out for lean.

A common problem was hamfisted peeps overtightening the mixture screw in, then the fine brass tip snaps off in the carb body prventing any change in the low speed mixture. my carb had both of these and got an engineering friend to "push" them through. It opened up the hole slightly but I just screw in the new screw more.

all the points do, is pass 12v to the coils for the appropriate amount of time (dwell). I did say do your timing first, assumming that the points gap was already initially set (which they are) then reset them after the timing

I would try it as you will get better acceleration. I had a similar setup and i was great. fuel consumption was worse and you tended to race other bikes/cars up to 80mph, so engine life would be shorter. I now run 1 tooth over just to tame my red mist

do the timing first, then reset your points. invest in a Xenon strobe £20 off ebay.

I'd also get a parts book, as this illustrates all the parts and you can phone suppliers with parts numbers. I have haynes, Clymer and Yamaha manuals which differ in their presentation. I would say Yamaha manual to have the most information with torque settings and diagnostics etc

Carb issue, pilot jet

the balance pipe in the xs400 was to effectivley lengthen the pipe so they (yamaha) could fit a shorter silencer to get the look right and still comply with the regs.

Just google "engine wise" and the top search is the kit!! I thought that if you could seal the area around the pet cock after t has been removed and pour in the solution into the tank, you could achieve the same result. I have used this method on brackets etc in a bath and it will remove the paint. It also get hot depending on how much you insert the cathode (stainless rod) you do this at your own risk BTW don't come back to me with tales of woe

I didn't know till this post!! I had gone at 4:40 to beat the crowds so fortunatly didn't witness it.

the oil light should be off!! that means if you have no oil in your tank then the engine is partially seizing. check your oil first

I just got home from Tractor pullin' in Gt Eccleston Nr Blackpool If you like engines, just look at this 8500 hp from 5 V8's also jet engines a plenty

code information from your engine or frame number here try speed and sport

you could always try this and engine wise do a lay-up kit

should not have any sparks jumping the points, your condensor has gone if it does!! the points share a live feed which when closed "charge" up the coils. to check your coils 4 ohms and 9.5k ohms should be measured on your coil wiring +/- 10% or swap over if one side is working. I had problems with my bike bogging down under 5k revs and then trying to go over this. new plugs (iridium) cured this. did you use the correct timing marks on the rotor? always use a strobe as when you tighten up the points the damn things shift, so i have to compensate so when it tightens up they are spot on.

Far as I know fuel is not hydroscopic (like brake fluid) water is present in the air (and in tank) and condeses. As water is heavier than fuel it sinks and guess where your fuel tap is? that's why tanks are rustier at the bottom. drewpy

if you can post a pikkie of the decals I can maybe tell you where you may get them. Its just that ther are about 4 different types for different countries and year!! Post Script: found this on ebay but there is a 4th version,( I know as my friend has them on his)

check out spark plugs to see if they are rich, I doubt they are. I have a feeling that you have some crud in your carbs especially the pilot jets as they give the rpm idle you describe. The only fix is to strip and ultrasonic clean the carbs and fit new jets whilst your at it. get the keyster kits from ebay http://www.siriusconinc.com/rebuilding_tips.asp

I might have a used set but you don't say what size rings as there are oversizes!!!

for sohc models inlet 0.08 -0.12mm ex 0.16 - 0.20mm

0.3 - 0.4mm

I use a semi-synth 4T oil and change every 3000 miles with a genuine yam oil filter.