drewpy

oil low and frothing at higher revs?

I'd start with stock and run on a dyno to get the fuelling curve. then you can optimize the flow with new jets if need be.

same thing happened to mine, I got a friend to look at them and he pushed them through from the top. It enlarged the hole but you just screw in the pilot screw in more!

Wow those carbs were gunky!! Mine were no where near as bad and i still had a severe blockage in which you describe. Had to soak over night and use a fuse wire and jiggle till i got compressed air through the bowl. Then i sent off to JRS to have them cleaned. Looking at my manuals, the pilot system can't be fed direct from float chamber as it has a blanking plug over the jet so would seem to come off the starter system!! The fuel filter you have is the same as mine. I thought they had a paper element at the top part!!

Watch those balancer chains and tensioners, and keep the oil clean as the top end gets starved of oil easily

I just used a small inline paper filter. Just because they are ultrasonically cleaned, doeasn't mean all the crud is out. Some swear by using a carb additive in the petrol tank and that clears out the gunk

on my xs400 the timing marks are called RF for right LF for left. The LT/RT etc is for the valve timing. just a thought

http://www.cmsnl.com http://www.bikebandit.com http://www.yamahaspares.uk.com/index.html http://www.oldbikebarn.com http://www.nwvintagecycleparts.com/ http://www.hvccycle.com/ http://www.yambits.co.uk/ http://www.motoward.co.uk/ http://216.168.60.165/speedandsportinc/index.tpl http://www.cameron-site.co.uk/nrp/ http://www.sunrisegraphics.co.uk/

yep, pilot jets blocked ( a recurring theme in xs400 threads)

redwhite is the + feed from ignition swtch and connects to both coils. Grey and orange go to the conacts via condensor. the connector must be faulty or just needs some contact cleaner as they can get verdigri and prevent contact.

as from an xs400D, custom models have 16" rear wheels, high rise bars, different frames to accomodate a different seat. engines are the same maybe minor diferences in '80 with rubber mounted engine and oil sight glass.

coil primary resistance = 4 ohms (small wire and ht lead) secondary resistance 9500 ohms (small wire to other small wire) check ht cap not cracked and has continuity from lead

pilot jet blocked ,also check twin contacts (if fitted) to check timing/gap

either running very weak (check sparkplugs) or your ignition has somehow retarded. don't keep running it like that as you are getting partial seizures ( cutting out), does it run when cooled?

try asking here http://www.tr1.de/

I get the same measurments on mine and you should have 34mm carbs which are the same as the 400 so your good to go. A rebuild cost; get a keyster kit from ebay (canadian company) and send the lot off to a ultrasonic cleaner who does carbs (150$ ish)

take measurements and I'll check my 400 ones

any 34mm carbs should fit except 2 stroke ones (i think they are designed different due to the 2 stroke oil, but don't quote me on this) need to put on a dyno afterwards to get the fueling curve right

Chris, do a search on the forum as there's loads of stuff here. pm me if you are still wanting!

ho ho ho !if you ever find one NOS good luck!! rare as rocking horse do do's

the engine number indicates an xs650b '74 to 1975 but these had calipers behind the fork leg. The earlier 1972 XS2 had their caliper fitted at the front on the right side (viewed sitting on the bike) a swapped front end due to a collision could have happened in the past.

You're running too lean, screw in the air screws on the front of the carbs by equal amounts. If that doesn't help you need to check your connections from carb to cyl head and maybe look at buying new carb inlet rubbers as they crack with age and petrol (gas)

should do, both are 34mm mikuni's

in usa = 1983 Yamaha XS400K found this on motogrid for you http://www.motogrid.com/pages/parts/viewby...d/2/yamaha.aspx enter the above date etc and the service data there as well as part numbers. it is also known as 12n model which was very popular in Germany, which is where you will see most parts on ebay. http://translate.google.com/translate?hl=e...hl%3Den%26lr%3D uses google translator, you can pick up what they are on about (usually) unless you speak german and then you're quids in ) drewpy