FJ1200 carb spitting

[km4hr]

...
Like several people suggested I feel the carbs are too lean. But I don't know how to make them richer. ...

Did you check the float height on the spitters?  angle of the dangle and all that..

Unfortunately, I have forgotten to do that every I've removed the carbs for cleaning. Definitely need to do that however. But what are the chances that all four carbs have that problem?

Looks like I'll be removing the carbs again to blow out the ports with compressed air. I check float height then.

thanks

[weymouth399]

If you take them out, do yourself a favor and get 4 factory mikuni #40 pilot jets. You will be amazed how much better it will run. With a 155 air jet.

Bob W

[Travis398]

Do you have a pipe on the bike? and what size pilots?

do yourself a favor and get 4 factory mikuni #40 pilot jets.
Bob W

+1

[racerrad8]

do yourself a favor and get 4 factory mikuni #40 pilot jets.
Bob W

Actually, the aftermarket jets with the external holes in the body are less susceptible to clogging and can be found here; Pilot Jet

Randy - RPM

[Travis398]

Sorry I should have deleted that part from my quote.

I was pushing the larger #40, not the manufacturer.

[km4hr]

If you take them out, do yourself a favor and get 4 factory mikuni #40 pilot jets. You will be amazed how much better it will run. With a 155 air jet.

Bob W

Bob,

I like your suggestion. Apparently others do too. I'm going to order the parts tomorrow.

I'll be ordering the jets from the RPM web site that Randy posted.

I discovered another interesting part on the RPM web site that could be relevant to my problem. RPM sells an O-ring kit. The kit includes "intake manifold O-rings". My engine doesn't have O-rings between the carbs and the intake manifold. Is it supposed to? My carbs fit very tight into the rubber intake manifold. Not sure why O-rings would be needed. Maybe the O-rings go between the intake manifold and the cylinder head. Anyway, maybe they are leaking and need to be checked, whereever they're located.

Here's a picture of the RPM O-ring kit: http://www.rpmracingca.com/proddetail.asp?prod=carbkit

BTW, my bike is actually a car. It's a retired Legends racecar. It hasn't been raced in years. It's mostly used for putting around a parking lot. It rarely runs much above idle which may be a problem itself. I assume the #40/155 jets will work in a Legends car.

I'm not trying to make the car run well at high speed. Just the opposite. I need it to run smoothly at low speed.

You guys are great! Thanks again for all the help.

[andyb]

I discovered another interesting part on the RPM web site that could be relevant to my problem. RPM sells an O-ring kit. The kit includes "intake manifold O-rings". My engine doesn't have O-rings between the carbs and the intake manifold. Is it supposed to? My carbs fit very tight into the rubber intake manifold. Not sure why O-rings would be needed. Maybe the O-rings go between the intake manifold and the cylinder head. Anyway, maybe they are leaking and need to be checked, whereever they're located.

You're correct.  They're intake orings rather than carb orings.  They fit between the rubber intakes and the head itself.

[km4hr]

Do you have a pipe on the bike? and what size pilots?

do yourself a favor and get 4 factory mikuni #40 pilot jets.
Bob W

+1

The bike is actually a car, a Legends race car. No longer used for racing. It only does light duty putting around parking lots, mostly running at or just above idle. It doesn't need high power or high performance. I just needs to run smoothly at low speed and growl when you goose it, but instead it sounds like a Fourth of July fireworks celebration.

[km4hr]

Here's the latest news in the long saga about my FJ1200 engine. I installed #40 pilot jets as recommended by several readers. That seemed like a great idea but the carb spitting problem is still there. Now the engine is hard to start as well. It's apparently not getting enough gas, even with the choke on. It fires immediately when I spray carb cleaner into the carbs. Maybe the float levels are too low. Setting them is beyond my capability however.

I see places on the internet that sell carbs that have been overhauled and calibrated. If I knew that would fix the problem I'd consider laying down the cash. I don't want that expense without a solution however. I'm afraid something else is wrong like bad valves or an ignition problem.

I'm ready to admit defeat. I need a good mechanic in the Columbia,SC area. Any suggestions? Should I take it to a Yamaha dealer?

[Klavdy]

I'd pull the carbs and send them to Randy for a clean and overhaul.
Either that, or if it's just used as a toy hauler in a car park, new manifold and a Holley 350 single carb type of deal.
One thing that absolutely would fix it right up is bring it to a Rally.

[movenon]

Please forgive the dumb question. What is the symptom if the diaphragm/diaphragms are leaking ? When I rebuilt my carbs as a check I blew into the oblong hole feeding into the (actually below)  diaphragm area and MUCH to my surprise 2 out of 4 leaked. The diaphragms did not have any holes in them, they they just would not seal good probably due to the age and crushing of the built in O ring seal.. I took each diaphragm cap and with some 400 grit sand paper and a flat surface "trued" up the caps. Still took a few tries to get them sealed. 
At any rate if anyone rebuilds there carbs I would recommend the "blow" test. You should blow into them and have the slide snap right up.
And replacing the O rings between the plastic intakes and the head, I would call a must do while there. They are cheap and with a leaky one you could end up burning a hole in your piston or cyl..
Just passing along what I found with my carbs..
P.S. no comments on "blowing" your FJ           good day

[km4hr]

I'd pull the carbs and send them to Randy for a clean and overhaul.
Either that, or if it's just used as a toy hauler in a car park, new manifold and a Holley 350 single carb type of deal.
One thing that absolutely would fix it right up is bring it to a Rally.

Interesting idea! Is a manifold such as the one you mentioned available?

[Klavdy]

Yes mate, I've seen one made by 'Lynx" , it was for a turbo application and of course there are a lot of other turbo adaptor manifolds for single carbs.
I dare say our mate Randy would know a fair bit more about the practical applications of one for a non turbo motor than I would but I reckon it would work pretty well for it's intended use.
Putting about the carparks etc as a toy hauler, plus you have the added benefit of body work to hide stuff behind.
Whaddya reckon Randy?
Where a loss of power is not an issue, would you use a single barrel Holley for easy , low speed drive-ability?
I know it goes against the grain, but for just cruising about the lot, this type of setup could be a goer, eh?
This may be an interesting build.

[SlowOldGuy]

The diaphragms will slowly leak down during the blow test.  There is no seal between the slide and the carb body, but it is a close fit, so pressure will slowly leak past the slide below the diaphragm.  Another thing that will cause leakage during this test is the choke plunger.  Make sure the rubber seal on the end of the choke plunger is in good shape, or make sure the plunger is all the way shut.

DavidR.

[bcguide]

Have you checked your valve clearance? I would be looking at that and the plug wires

Scott