Author Topic: Plz Help- Carb problems (I think I'm going mad)!!!!! (Read 3910 times)

bubbazenetty · « **on:** August 09, 2006, 08:46:08 PM »

Ok, finally after getting the ignition ECU(ECU was fried, and I got a replacement from the UK) and the coils working properly(one coil was failing when it was hot) I find out that my little 400 isn't firing on the 2 middle cylinders at idle up to about 6k rpms. Over 6-8k rpms it's firing on all 4 cylinders. I check for spark, and yes I have spark. I then disassemble the carbs, clean them completely and notice that the plugs for the pilot jet is missing on those 2 carbs. I went ahead and put non-stock rubber plug in there tightly and reassembled. Now I put it all together and when I fire it up again, then only one carb isn't working...but then about 2 minutes later it stops working!!! The pther carb still won't work. I'm stumped.

I've redid the carb cleaning on the 2 carbs that aren't working, by completely disassembling those carbs (including removing the emulsion tubes and pilot jets) and blowing all orifices out with carb cleaner. They look clean and I'm getting good airflow thru all the orifices. I've even went so far as to check the diaphrams by sucking on the bottom of the carbs, and yes the diaphrams are pulling up very easily.

I'm 99% sure that there is something wrong with the idle and low rpm circuit of these 2 middle carbs...but I just can't figure out what it is!!

If anyone has encountered a similar problem...and has figured it out, please let me know.

I'm at my whits end...and if I don't figure this out soon I'm going postal on this damn bike.

Please help.

Ps. Bike has good compression on all cylinders and plenty of fuel in all float bowls.

BrianM · « **Reply #1 on:** August 09, 2006, 08:59:33 PM »

2 things - spend the $20~25 to replace all the o-rings and plugs with OEM replacements (or at least with stuff that's not damaged by fuel).

Second, Clean the carbs. You wouldn't expect your teeth to get clean by just blowing air over them, or just rinsing with mouth-wash (carb cleaner). You clean the surfaces with a brush and the crevices that a brush won't reach with floss (use copper wire and Only copper - it's the only metal that's softer than the carb parts and won't damage them.. I pull mine from 12~14 guage electrical wire).

Between those 2 things, you're 99% likely to have a positive resolution.

interfuse · « **Reply #2 on:** August 09, 2006, 10:28:02 PM »

FYI, I had the same problem when the wiring going to the ignition coil from the wiring harness was failing. Wiggle the wires going to the coil (#2 and #3) from your wiring harness and see if it idles. I pulled on the connectors and one of my wires literally was broken, causing intermittent connections. At higher revs it seemed to be able to either jump the break in the wire or the wire would shake into place making a connection, and seem like it was running on all 4.

If that's your problem its simple to fix. Go buy some crimp spade connectors cut the wire back 0.5 and inch and you're good to go.

onenicebandit · « **Reply #3 on:** August 09, 2006, 11:18:13 PM »

Sounds like a combination of o-rings and air leaks. Mine still isn't running good. It starts up reluctantly with a little bit of gas, and after I rev it for about a minute, the idle comes up to 4k and never drops back down. It seems like it running on all 4. I had it going a little over 100 and it does get up and go awfully fast. I'm thinking it wouldn't go that fast if it was running on 2, I think it would actaully run like a terd on 2 cyl's. I'm planning on taking it apart on Friday and figuring it out.
A quick ? for 4 owners; going down the road in 6th gear, is it normal to be revving at say 6k at 60 mph, 7k at 70. That's what it seems like on this bike, it seems like the R's are a little high, but I do understand it's a 400. Let me know.

bubbazenetty · « **Reply #4 on:** August 09, 2006, 11:20:53 PM »

Brian, I'm going to totally remove the carbs one more time and clean them again, and run a small copper wire thru all the orifices..then I'll try again, and let you know what is going on. I'll also install all new O-rings, but the plugs that I have now will have to do, as the originals aren't available from a dealer. I'll try to source some later.

Mike, the 2 coils I have are used (but in good condition), and the left side is connected to sparkplug#1 and #3, and the right side one is connected to the sparkplug #2 and #4, so I'm not exactly sure if there is a problem there??? I'll check the coils again, but always when I've checked for spark I've gotten a great good spark....so that is what is leading me to believe that the issue is fuel related.

Thanks guys.

Ps. The way I'm checking for a good combustion is by spraying water directly to the exhaust header of each cylinder...It's noticable that the water doesn't eveporate rapidly when there is NO combustion in that cylinder.

gsxr400 racer · « **Reply #5 on:** August 09, 2006, 11:38:53 PM »

rubber plugs are still available try a newer year and they used them same plugs on gsxr carbs and katana's like 600-1100 stuff

interfuse · « **Reply #6 on:** August 09, 2006, 11:49:13 PM »

Quote

the left side is connected to sparkplug#1 and #3, and the right side one is connected to the sparkplug #2 and #4, so I'm not exactly sure if there is a problem there??? I'll check the coils again, but always when I've checked for spark I've gotten a great good spark....so that is what is leading me to believe that the issue is fuel related.

Check the maunal section 8-16. #1 + #4 (left coil) and #2 + #3 (right coil). But I don't think you'd even get it running with the plugs messed up.

I thought I had a bad coil, turned out it was only the wiring going to the coil that went bad.

gsxr400 racer · « **Reply #7 on:** August 09, 2006, 11:51:54 PM »

yep it will run like that but like ass!

gsxr400 racer · « **Reply #8 on:** August 09, 2006, 11:56:45 PM »

Let me explain some theory here all in line 4's are wasted spark motors this means unless you have independent timing if one fires then cylinder 4 is also firing it may not need that spark or be on the right stroke but it still fires for them to fire individually you would need like coil in the cap like on new gsxr's so if you are ever putting coils on and cant remember where the plug wires go you can always hook up 1 and 4 together (any motorcycle inline 4 and 2 and 3 to the other coil if it doesnt start right up or backfires switch the lead wires to the other coil , Get my drift?

bubbazenetty · « **Reply #9 on:** August 10, 2006, 12:02:44 AM »

This could be my problem all along....I'll update this tomorrow....after I switch the plugs.

Thanks again guys.

bubbazenetty · « **Reply #10 on:** August 10, 2006, 08:21:57 PM »

Well I was wrong on the sparkplug wire location. Left coil is on cyl#1 and #4 and right coil is on cyl #2 and #3. That rules that out.

Took the carbs apart for the gazzillithion time, and use a small copper wire thru all the orifices as well as a full can of carb cleaner...and put it all back together.

Start it up, and sure enough the two middle ones don't have any combustion at idle and up to 6-8k rpms.!!!!!!!!!!

This is driving me nuts.

I've got good vaccuum on all cylinders (all are fairly even on the carb stick).

So I'm completely stumped!!!

Any1 have any other ideas????? Pls let me know.

stormi · « **Reply #11 on:** August 11, 2006, 07:34:50 PM »

Switch your coils? (not just the wires)

Make it so that 2 & 3 fire from the left coil, and 1 and 4 fire from the right? If it's still 2 & 3 that are a problem, then you're likely looking at a carb problem. If it changes now to 1 & 4, then the coil is more than likely at fault.

bubbazenetty · « **Reply #12 on:** August 12, 2006, 05:22:12 PM »

Just switched the coils....same problem.

Any1 else with any ideas????????????????