Running rich

[PaulD]

My Kat is running really rich, so rich that it doesn’t need choke even on the coldest mornings and if I try to use choke it just kills the motor. The plugs are black as a badgers bottom and sooty as hell.
I’m going to pull the carbs off it and have a poke around to find out what’s amiss. I’ll stick em in the ultrasonic bath and give them a good clean while I’m at it. Are there any pitfalls I need to avoid while removing and replacing the carb banks from the bike and any known issues when I get inside them?

[Kryten]

Removal and refitting is a bit tricky. Remove the air filter housing from the bike. Release the clips on the inlet rubbers and the carb to plenum chamber. Slacken the 2 long screws holding the plenum chamber in place and pull it rearwards.
Re-assembly is, as they say, the reverse of disassembly but a bit of warmth on the rubbers and your preferred spray lube will allow the carbs to reconnect.

I have always worked from the right hand side of the bike to remove/refit. Try and roll the carb bank clockwise into the bottom of the inlet rubbers and the top of the plenum chamber rubbers (if that makes sense).

Using a piece of wood through the air filter hole to push the middle of the plenum chamber up to the carbs will help them seat properly.

The use of strong Anglo-Saxon phrases also seems to help but it has yet to be proven scientifically.
Skinned knuckles are also considered to be mandatory.

When they are apart a good session in an Sonic Bath should sort them out. Rebuild with viton O rings (Uncle Bob has a link to a supplier) to avoid ethanol degradation. Careful setting of the float heights is worthwhile. If it is running rich it could well be float valves being sticky or worn. So new float valves and seats while you are in there.

Do a leak test on the bench when they are re-assembled, I used some 2 stroke mix for a chain saw on mine as it was a fairly visible pink colour to show any leaks.

They will need a balance when you have them re-fitted. So valve clearances should be in spec as should the ignition timing.

Good luck

[Kryten]

Oh and don't forget to use your JIS screwdrivers...........

[PaulD]

Oh and don't forget to use your JIS screwdrivers...........

Well I would if I had any
I’ve got a set of slightly modified Philips drivers I normally use.

[PaulD]

A good few hours spent on the beast today removing the carbs and stripping & ultrasonic cleaning the first two. I removed the air filter box first only to find I didn’t need to ah well I took the battery out and put it in trickle charge while I carried on removing the carbs. As I was told this isn’t the easiest of jobs and plenty of swearing was used to aid removal. I can see it’s going to be a real pain putting them back on the bike. I’ve stripped the first two carbs and apart from being filthy outside they looked pretty good internally so I’ve not found any obvious reason it’s running so rich? I’ve scrupiously cleaned the float valves and made sure the choke plungers are seating properly plus I’ve checked the float heights and main/pilot jet sizes and everything’s as it should be. I’ll finish ultrasonic cleaning the remaining two carbs and put everything back on the bike tomorrow and see how she goes. Fingers crossed.

[PaulD]

A bit of further digging has revealed a problem, although I can’t see how it would make the bike run rich?
On the inlet/engine side there is what I think is an air bleed screw the point of which protrudes slightly into the carb venturi. This screw is 3 1/2 turns out and has a tiny O ring on the pointed end, this O ring is looking very much the worse for wear! Are these available or are they included in the kit uncle bob recommended?

[PaulD]

Well panic over, temporarily at least I’ve found some O rings in my stock the correct size to fit the mystery air bleed screw and although they’re not Viton they should be ok for now. I’m going to order A Litec carb kit and totally refurb the carbs at a later date. I’ve also replaced the O rings on the fuel connector Stubbs and breather hoses while I’ve got the carbs off. Again they’re not Viton but they won’t be on there long so I should be ok. I’ve even got the carbs back on the bike which was actually easier than getting the buggers off in the first place. Tomorrow’s jobs are fit all the hose clips and generally reassemble the whole shebang. Fingers crossed I’ve sorted the rich running problem

[Uncle Bob]

Sounds like the pilot screw and yes they are in the LiteTek kit (Pilot Screw O-Ring OR-005). I have added the Carb specs section from the manual for the SD so you can compare numbers and see if yours match or are indeed different.

UB

[PaulD]

Brilliant thanks for that Rob, I’ve saved that chart for further use. All the bits in the carbs are as shown on the chart so there doesn’t seem to be any problems with previous owners “improving” the carburation. Even the float height is correct!. Just have to see if things have improved when I start her up tomorrow.

[Kryten]

This link will help de-code the E numbers

https://www.motorcyclespareparts.eu/suz ... ation.aspx