Carb tuning help

[JohnnyW]

Next I could do is to push the whole bike into the sea. 

Yep, that's how I'm feeling.

[Pat Conlon]

Weird thing this time is that downpipe 2 and 4 (looking from seat) got hot, but 1 and 3 didn't, so that kind of eliminates a coil problem (clutching at straws here), but I suspected my new plugs (*clutch, swipe*), so put my old ones in 1 and 3. Tried again, and this time 1 and 2 stayed cold, so didn't fire at all. Not electrical I think.

Johnny, if you changed the plug on #3 and now it gets hot, it sounds like you are on to something.
Just so our terminology is correct:
Sitting on the bike the #1 cylinder is on the left, #4 is on the right.
The left coil should be connected to #1 and #4 plugs, the right coil goes to #2 and 3.

So if you changed any plug, and now that cylinder is firing, you have an electrical issue.

[JohnnyW]

Thanks Pat, but I'm not convinced that's the issue, as each pot was on an individual coil, and why would this suddenly fail - Coincidence? Nah, I reckon I have done something wrong.....

To back-track a little, I embarked upon this as my bike is rarely ridden, and it's a miracle it has never given me any trouble in the 22yrs I have had it, given how often it is sitting idle. My bubble burst  a few weeks ago, when I got fuel pissing out of the overflow over my feet, suggesting a stuck float/needle, and no amount of banging it would coax it free. After coming home on the recovery truck, I decided to do the strip/rebuild of the carbs.

I have never had any issue with anything other than the tank rusting through, which I have replaced with an ugly but functional one for the time being. I replaced the spark plugs and changed the oil and filter whilst doing this job, but as I say, have had no running problems previously.

So, what might I have done wrong? I may have mixed up different carb parts, but I put new needles and seats in, so surely everything else is really not carb specific? I checked the float heights. I cleaned everything with carb cleaner, soaked the jets, and blew it all through with a compressor. I took my time. I followed the instructions on the sheet from Mr.Rafforth, along with a few other tutorials on the web.

Soooo,

What I am noticing now is that she fires first push, revs relatively high, then dies, and won't respond again until I have left it a while. I have an auxiliary fuel supply, gravity fed. but it does suggest that fuel 'gets through' somehow, burns off, then it doesn't get enough after that? When I could get it to kind of run previously (I have had the carbs off three time now!), it was very lumpy, and would only run on choke.

I am loathe to just take them off again, and do it all again, as it's such a wrestle to get the airbox etc back on, and mainly because I am just going over old ground. I suppose my question is what can I have done to make it so bad?

[Pat Conlon]

Where did you get the carb parts? Did you get the correct float needle assemblies for your fuel pump carbs? http://www.fjowners.com/index.php?topic=9836.0

If you are sure it's not a spark problem (with a plug swap, why would #3 start working?) the only other thing I could think of is that your idle circuits are not clean.i

[FJmonkey]

What I am noticing now is that she fires first push, revs relatively high, then dies, and won't respond again until I have left it a while. I have an auxiliary fuel supply, gravity fed. but it does suggest that fuel 'gets through' somehow, burns off, then it doesn't get enough after that? When I could get it to kind of run previously (I have had the carbs off three time now!), it was very lumpy, and would only run on choke.

Reading this part of your problem description sounds to me like the carbs are feeding too much fuel. It is really hard to diagnose this way so this my stab at it. Having to wait "won't respond again until I have left it a while" is my primary reason for thinking of flooding. The other reason is only running on choke, but that could be that the engine won't run long enough to warm up. Before this gets too frustrating you might consider sending the carbs to RPM. Everyone that has reported the bike running really well after the carbs got some RPM mojo...

[JohnnyW]

FJMonkey and Pat...... I checked that I had got the correct carb set crk062, as provided by Yambits UK, covering models 1988-92, but what I haven't done is compare them to the ones I took off. My 3CV has a fuel pump, not gravity feed Pat, so I need the smaller orifice.

This would explain my issues wouldn't it, if I had the wrong size ones, but I am not sure it's likely, else everyone else who bought the kits off Yambits would be wrong. I am going to get them to check tomorrow, saving me having to strip them out again, but I reckon I may end up having to do it again anyway, and start from scratch.

Thanks for your help - It's nice to just get out of the garage and talk to people!

[racerrad8]

I checked that I had got the correct carb set crk062, as provided by Yambits UK, covering models 1988-92, but what I haven't done is compare them to the ones I took off. My 3CV has a fuel pump, not gravity feed Pat, so I need the smaller orifice.

That looks like the K&L kit sold here in the US. Look at the side of the brass seat and there should be the size (1.5 or 2.3) stamped into it.

Randy - RPM

[Pat Conlon]

.... My 3CV has a fuel pump, not gravity feed Pat, so I need the smaller orifice.

Yea, I saw that. that's why I went back and edited my post to you.
My mistake was that I went to the first post in this topic by a different member (balky1) and thought we were talking about his "85.

I you have the larger float needle set (gravity flow) you will be flooding your bike.

[JohnnyW]

I checked that I had got the correct carb set crk062, as provided by Yambits UK, covering models 1988-92, but what I haven't done is compare them to the ones I took off. My 3CV has a fuel pump, not gravity feed Pat, so I need the smaller orifice.

That looks like the K&L kit sold here in the US. Look at the side of the brass seat and there should be the size (1.5 or 2.3) stamped into it.

Randy - RPM

Thanks guys - Yeah, I can see the size on my old seats, 1.5mm, but obviously the new ones are in the bike, and I don't want to take them out if I don't need to, i:e They are correct. I have mailed Yambits to see if they can confirm it before I strip 'em yet again. That said, if they are wrong they need to come out, and if not, I am gonna have to go back over everything again anyway, aren't I, so it looks like they'll be out again tomorrow.....?

[racerrad8]

Just to confirm you set the float level, properly and not compressing the needle spring, when you replaced the N&S.

Randy- RPM

[JohnnyW]

Just to confirm you set the float level, properly and not compressing the needle spring, when you replaced the N&S.

Randy- RPM

Well I thought I did Randy, but that's the sort of thing I am going to double check when I get them back off again. Thanks

[FJmonkey]

Just to confirm you set the float level, properly and not compressing the needle spring, when you replaced the N&S.

Randy- RPM

Well I thought I did Randy, but that's the sort of thing I am going to double check when I get them back off again. Thanks

Having the UNI pods makes the carb removal much less of a  task

[JohnnyW]

Having the UNI pods makes the carb removal much less of a  task
[/quote]

I thought I might, but having read another FJ site, this chap felt the lack of support from the air box meant the carbs vibrated more, could lead to the manifolds splitting, and also you need to rig up a crankcase breather filter too, and that gets very oily. Thoughts? Experience? I am all for improvement, but I don't want to create myself some more problems.

[TexasDave]

I have unipods on my FJ. As short and stiff as the rubber manifolds are I don't forsee any problems with them supporting the carbs. In the old days before air boxes,  manifolds supported the carb and an air cleaner as with singles and twins. If your manifolds are cracking it is time to replace them. Heat and old age make them brittle. They are rubber to reduce the heat and vibration from the cylinders to the carbs.  Dave

[FJmonkey]

rig up a crankcase breather filter too, and that gets very oily.

The breather is quite easy. A hose just long enough to put the breather filter in between and just under the two pods. When the engine is running the oily air is in the air flow and sucked back in, much like the air box connection. When I get a chance I will pull the seat and take a photo, and see how oily it is under there.

Crank Case Breather