Carb xj900 31a

Very quick question, will the carbs from a 853cc xj900 31a fit a later 891cc xj900 58l
Obviously they will need rejetting and setting up but what I am asking is are they going to mount on the carb stubs and ilet rubbers or would thlose need changing?

 

I think the main difference is that the 58L had 36mm versions and the 31A used 35mm inner bore. Other than that, the carbs look the same from the outside and should be physically compatible.

My experience comes from the PO bodging one of the carbs on my '83 and trying to replace just that one carb with a 36mm version. Might have actually worked had he not kept the 35mm slide. (other than likely being impossible to balance)

But really looking at the two side by side it's hard to see any difference. The 31A will probably flow less mixture due to being a smaller bore, so you might lose a little power.

 

Thanks, was a set on ebay uk for £29.99, should have bought them price has now changed to £499.99......
On two of mine a float bowl pillar had been broken so had to cut them flush, make new pillars and reset floats, all seemed good, no leaks for a while
Just did not want to waste money on something that would not fit, mine were ok for a week now leaking and full of rust despite using 2 filters in fuel pipe. Drained fuel, again water in fuel. Was fresh in a dry tank last week.
Getting depressed about this bike, to the point of sending it to the scrap man if I cant get right soon

 

How did water get into the system if you cleaned the tank and the cap is sealing? Did you de rust the tank? You should clean the carburettors again and try plastic auxilliary tank to keep everything clean. Did you split the carb rack? Debris in the T inlet between carburettors 2 and 3 and the attached pipe would be below your filters. If it is there are moved that could be the source of your problem. You need them clean and use an auxilliary tank to establish that the needle valves are sealing, you also need to check the float levels. Some owners have to remove the carburettors a few times to get them right. Don't quit plenty of help here. You repaired the float posts so the rest is easier just might take a little time to get right.

 

Not sure what glue you used to fix the broken pillars but I have mastered the art of tig welding them if you need a repair. Ditto @Franz comment on the rust and water, you obviously didn't do a good enough job the first time

 

No glue used, bodies were drilled and tapped new pillar were made with threaded ends and screwed in, tank was cleaned and dried left in storage container in hot weather for a week.. Had bike running on auxilliary tank all was good had it running, checked everything was good then replaced bike tank with fresh fuel in, to take for run and back to square one,
Spent morning swilling tank with fuel picture shows some of what is coming out, looks like failed liner. maybe water was trapped behind liner?
Am told that petrol station has had complaints about water in fuel, although they deny it, only petrol station in about 5 miles that was open.

 

So your carburettors were good running off auxiliary tank. Most of that tank debris should have been caught with the filters. That's unfortunate if it is a failed tank liner. I heard MEK can remove it. Cheapest method if it is not a tank liner fill the tank with vinegar for a few days or electrolysis. Put a magnet over that debris out of the tank see what it lifts.

 

Tried that, asI thought a magnet in tank might attract debris but no good checked rubbish coming out of tank also not magnetic, also just put fuel back through tank, this time drained it through tap, and inline filter that was on bike am getting debris coming out with fuel , so looks like filter has failed allowing debris into carbs.
Looks like I'll need to clean failed sealer out, probably reseal and then refit with new inline filter.

 

Do your filters have direction arrows for fuel flow? Must be sealer then that's a bummer it has failed. There are 900f tanks on E bay if you want to get another one?

https://www.ebay.co.uk/sch/i.html?_...570.l1313&_odkw=tamaha+xj+900f+tanl&_osacat=0

 

Filter has directional arrow and were fitted in right direction, have a tank that was fitted previously, but has leak in usual place, bought this tank from facebook a while ago was told it was good, does not leak but been having problems since fitted, getting worse. Have MEK ordered, so will use that to try to clean tank then it will need probably need repainted and probably resealed but in meantime will clean carbs again and try a temporary seal on old tank with araldite.
Have also ordered a 30micron sintered bronze cleanable fuel filter. Can you get replacement filters as fitted to the fuel tap the one inside the tank had a search but could not find one

 

Have you tried Fowlers Yamaha?

https://www.cmsnl.com/yamaha-xj900f-1991-4bb1-europe-214bb300e1_model38004/partslist/0028.html

They only sell the full assembly. Better getting a used one on ebay.

 

The curse of the previous owner (PO).....
When it comes to carbs these things have to be spot on, anything else you have problems.
A few yrs ago I was having low speed/low load misfire issues with my road car. I tried a tankful of Shell super unleaded from a different garage and it improved no end, but came back again on resumption of my usual fuel supplier.
When I looked in the tank I could around a half a pint rolling around in the bottom, had o make up a suction jar to physically suck it out.

 

More than once I had cause to be grateful for the makers fitting drain plugs to the carbs, because of water in the fuel.
That provision died off, of course.

Relatedly, I had an old Sunbeam that would periodically go into limp mode, long before it was a thing.
Turned out to be an old swollen fuel sender gasket scooting around the base of the tank and occasionally blocking the uptake pipe (no filter on the end).

 

@Paul mills

https://www.ebay.co.uk/itm/33619609...-a02c-9e4d553a1e97|iid:1|vlpname:vlp_homepage

Don't know if these are the ones you need but have a look anyway.

 

Cleaned carbs, little bit of water and a fair bit of gunk, pilot jets were blocked, runs ok on dummy tank, put fuel in original tank, found slight weep, reason I changed it, patched with araldite, I know it wont last forever, but will give me chance totake bike for a run when its set, "new" tank has a couple of litres of acetone in to see if that will clean it out, will leave that for a couple of days and recheck it if that does not work will try some mek to clean it.
Also fitted new filter inline, had a panic when I went to chuck filter box found filter element in it, checked filter, but one a!ready in, read label on packet andit says filter comes with spare element