2001 YZ426 Carb Issues

[olschl]

Just bought a used bike and going through and cleaning an extremely gunked up carb as the bike was sitting with gas in it for 18-24 months, if not longer. I think I have it all cleaned up but I also believe I have lost an o-ring under the cover of the accelerator pump. It appears there are suposed to be (2) o-rings under the cover and I seem to have misplaced the larger of the (2). Anyone have a part number for this o-ring or am I just as good going to the local hardware store and picking a close match up? I downloaded motoman's manual but the carb diagram is of so low resolution, I really can't make out what is happening under the cover. Also, are there full rebuild kits available for this carb? Any help appreciated as I really want to fire this bike off!

Chuck

[grayracer513]

One is labeled as a gasket (3TJ-14536-40-00). The other is called out as an O-ring (6H4-14561-00-00)

[olschl]

Thanks grayracer! Looking at RonAyers microfiche I see what I need. Another question I have is when reassembling, jets labeled #20 and #22 on the card breakdown are almost identical in size other than one has a squared off shoulder and the other has a tapered shoulder. I reassembled the carb with the squared off jet as #20 in the diagram and tapered jet as #22. Confirmation that this is correct would be appreciated.

Chuck

[grayracer513]

They are nowhere near the same size. Jet #20 is an air jet, and should be marked 200. It goes in the mouth of the carb. The other should be in the range of 62 to 80, and is the starter jet. It goes in the float bowl and feeds the "choke" circuit. If you can't read the sizes, the air jet is the one with the larger orifice.

Do you have a manual?

http://www.yamaha-motor-europe.com/community/service/manuals.jsp

[olschl]

Woohoo!! Got the bike running tonight and it starts first kick now. I seem to have to idle the bike very high to get it to stay idling and of course the header glows orange right at the outlet which, from what I read here, is normal. Bike run great through the throttle range and seems to have plenty of power but really, really pops on decel. I do have a Kawasaki ZRX1200 and am somewhat familiar with carbs and jetting but this flat slide is an entirely different animal. When I disassemble the carbs, I did not take apart the choke or hot-start assemblies, nor did I remove the pilot jet. Any suggestions on where to start. I know this is a rather ridiculous and open-ended question but given that everything else seems to be working fine, I thought someone might have experienced the same symptoms and had an easy fix.

Chuck

[olschl]

Using the search function, ? I found quite a bit of stuff on "decel-popping". My first question is, when people refer to the "fuel screw", is that the same as the pilot jet? Unless anyone has a different suggestion, my next course of action will be to take the carbs back off, remove and clean the choke and hot-start circuits, check where the pilot is set at, remove and clean it, check what pilot and mains I have in the carb, reassemble and see where that gets me. Also, the set screw at the bottom of the throttle cam is not adjustable in any way is it? I have it run all the way in as it seems where it was at before I tore the carbs down. Additional thoughts appreciated and I will be more diligent in using th search function in the future.

Chuck

[grayracer513]

The pilot jet and the pilot fuel screw (idle mixture screw) are two different things.

[olschl]

When people mention "adjusting the fuel screw", how is this accomplished and what does it do? I do not see a "fuel screw" listed in the carb diagram. BTW, thanks for the link to the higher quality manual!

Chuck

[grayracer513]

On page 4-8 of your manual, the pilot screw is #11.

Pilot screw adjustment is covered on 3-17. The screw is a trim adjustment for the idle (pilot) fuel circuit.

[olschl]

Well, a closer inspection of the carb shows the pilot fuel screw to be completely missing. I guess this explains the idle issue and back-firing. Would a dealer have this item? Is it unusual for the bike to run at all without the pilot screw? Anyone around Tulsa, OK have an extra? No luck at Cycle gear.

Chuck

[BRYANS01]

dont buy another stock screw buy a zipty that way you can adjust it by hand and dont have to fight with a hot motor and a tiny screwdriver order from the tt store it would only take a few days to get to your door. are you sure the screw is gone it sits pretty far up inside the float bowl you can only get to the stocker with a small screwdriver and by going by feel. also im a firm believer in the jd jet kit it will take alot of headace out of getting the jetting set up right.