Grashopr

Member
Feb 22, 2002
18
0
I have an issue. I've had my 01 426 now since March.

First, my riding history: I have attended 2 hare scrambles and have raced on an outdoor motocross track 4 times (2 motos per day, 5 laps per moto, plus a 12 min 'practice session' once per day). I have ridden the bike maybe 15 hours of actual 'play riding' at an ORV park in the local area. The oil was changed the day I picked it up, and every 2 weeks since (unless I didn't ride AT ALL during the 2 weeks...then I'd put it off for 2 weeks...if I even rode once during the 2 weeks, though..I change the oil and filter).

My mods: I put a UNI filter on about 2 months ago (before starting the motocross racing) and it's getting a bit dirty, but not horrible. I pulled the light-blue wire from the ignition plug connector.

Here's my predicament. I bougth the bike from Michigan in the wintertime. When I got it back to Kansas, it ran fine (it was still extremely cold outside). As it started to warm up, the bike started running more and more rich, and it started getting harder to start...so I took it to a local motorcycle park's fix=it shop and asked them to adjust my carb for easier starting and to fix a half-throttle stutter (when riding the bike at half throttle...it would choke up and stutter horribly). They adjusted my Pilot Screw and got the bike to where it was a little easier to start, but they didn't even try to take care of the mid-throttle stutter.

When I discovered this, I read through my manual and decided that dropping the needle one notch was my first plan of action. I had read on this forum that some people said that cleaning the carb's passages and jets may help with hard-starting also. So I decided to take the carb apart and clean it when I had the needle out. Moving the clip on the needle was simple...took about 5 min. But when I went to clean the carb, I removed the bowl off of the bottom of the carb, and cleaned it out using Urethane Reducer and Q-tips (it wasn't horribly dirty, but I cleaned all of the surfaces anyway). I then removed the bottom assembly of the carbeurator that houses the actual 'float' assembly. Below this were the needle, main and pilot jets. I started to remove these, one at a time to clean them. When I was done, I saw another copper-colored 'jet-looking' thing and decided to remove it to clean it too...it was the pilot screw, not a jet and I didn't find out how many turns out it was before I started unscrewing it. Once I realized what I was doing...I tried to put it back in, but I'm still unsure about where it was supposed to be. Well, luckily, once I got the carb back together, the bike started, but the idle was way low..so I screwed in the idle adjuster until the bike would hold an idle (it actually wont hold an idle...it's either over reving or dieing...but never a consistent, smoothe idle). I don't have a screwdriver small enough to fit in to adjust the pilot screw, and I was in a hurry to ride, so I loaded up and went riding.

Well, the bike runs okay, but it WONT idle at all...and after I ride it, if I use the kill button to kill it (don't let it die on it's own), it is NEAR IMPOSSIBLE to start again while hot. Not even using the hot start button will help it start. To get it to start hot, I have to pull in the compression release lever, kick it over real quick four or five times, then go through the normal 'starting ceremony', but whne I give it the 'money-kick', I have to give it gas for it to start.

So I took the bike back to the 'motorcycle park fix=it shop' again and asked them to adjust my pilot screw and see what was up with my mid-throttle stuttering (moving the needle down one helped it, but didn't fix it all the way). The owner of the shop started asking me if my valves had ever been adjusted. I told him no, but that the bike only has around 25 total hours on it and I was sure that it shouldn't need them checked yet. He asked me whether it had steel valves or titanium valves. I told him I wasn't sure, but that I thought it had steel. He said that if it had steel, that on some bikes the valves will bang up against the seats and actually dent the valve face, which would decrease the valve's clearance. He said that then, if the valve got hot..the clearance may be completely lost, and that would force the valve open just a hare when it's open...which would make starting it near impossible when hot. He told me to check my valve clearance to see if maybe this was it. I REALLY don't want to check the valve clearance before this weekend's race. Do any of you mechanics out there know what the chances are the at my valves are causing my recent starting problems, or is it just that I have my pilot screw in or out too far (and which do you think it is) and that's making the bike hard to start.

Thanks!

The 'Hopper'
Sorry about the long post.
 

Grashopr

Member
Feb 22, 2002
18
0
:think: I KNOW it's a long post..but I race on Sunday and I would like to know whether I need to pull my head off, or whether I should just concentrate on getting the carb straight and running it......HELP? :silly:
 
B

biglou

If I were you, I would put everything back to stock settings/jetting. I'm in KC so the altitude and terrain are not any different.

42 pilot and 1-1/4 to 1-1/2 turns out on the pilot screw. My manual is at home so I don't have the position, but I would put the needle back to the stock clip position. I've got a bone-stock 01 and it runs like a scalded rabbit from idle on up. I do have a little issue with a "hanging idle", but that doesn't bother me. And it starts first kick every single time unless I do something wrong like forget to choke it or pull the red knob or turn the fuel on! When I get home tonight, I'll try to post recomendations for jetting and needle clip position based on the manual.

Oh, the valves are titanium (only on the intake, I think).
 

endosports

Member
Jan 10, 2002
494
0
All the valves are titainium. After break in you should inspect the valve clearences. I don't have my manual but will post later the values.

If you have good compression, like if you can't kick the bike over without the compression release it is alright.

Checking valve clearence is simple. Time the bike to TDC( the little windows on the ignition cover) .

Remove the valve cover including head mounting brack to the frame.

Use a feeler gauge to check the clearence as so. To tight is extremely bad and the valves must be adjusted. To loose can damage your engine also.

Your valves are operated by overhead cams and shim and bucket contact.
under the bucket is the shim and the tickness of the shim is the adjustment.

Hope this helps. Search this site or thumpertalk.com for jetting tips. What is your altitude?

ENDOSPORTS :D
 

Grashopr

Member
Feb 22, 2002
18
0
I have NO idea what my altitude is...I'm in Kansas...it can't be very high...maybe 400-500 ft max. My compression is solid...I've developed a bad case of foot bruising from kicking the thing over (with alpinestars on even). It WILL NOT move at all without the Comp Rel lever after you bring it up on compression.

Thank you all for your info...but....I think I found out what the problem was though. When I took my carbeurator apart, I took the float bowl off, then removed the float from the lower section of the carb that I call the metering block (it has the fuel metering 'circuits' in it..one for pilot circuit and one for main circuit). Then I removed the 'metering block' from the bottom of the carb's main housing. There were four VERY small allen-head bolts that held this peice on, and Yamaha or Keihin had filled the heads of these with some sort of hard-pack epoxy that was apparently supposed to keep you from being able to get an allen wrench in there to take the peice off. Well, I took a pick and cleaned out the allen head bolts and removed the metering block from the main body...this block has the 'venturi assembly'...the peice that determines the size of the carb (38mm, 34mm...etc) and the same peice that the needle sits in and slides up and down through. When I removed this...there was a gasket that is very small and very intricate that seperates all of the passages for the pilot 'circuit' and the main 'circuit'. When I put the thing back to gether, this gasket had moved and fuel was getting from one hole in the main circuit area into the pilot circuit area...that explained the hard starting...EXTREMELY RICH!

WORD TO THE WISE: DON'T TAKE THAT PART OF THE CARB APART!!!!

If you check the carb break-apart diagram in your manual against the actual carb...it does not show that the carb comes apart there...it doesn't even show the bolts that I took out. If you go to Yamaha and ask them..their schematics don't show this part of the carb either..and they CANNOT sell you those gaskets...Sudco, Int (the distributor of Keihin parts to your local Yammy dealership) has gaskets for the carb, but as of today, they still aren't sure if they will fit, as the carb on our bike is not the same as the regular (HRC??) Keihin carb...our float is different and our throttle-rotator assembly is different. They are shipping the only gaskets that they have..but they had me call Yamaha...and Yamm USA said that there is NOONE in the USA that can tell me whether those gaskets work for sure or not...but if I could speak Japanese, they would patch me through to Japan when they opened up (sometime around 4am our time??) so I could ask them whether the gaskets were the same....so...if you decide to clean your carb...STOP AT THE FLOAT! Thanks again for your help guys.

Grasshopper
 

Grashopr

Member
Feb 22, 2002
18
0
Sudco's gaskets should be here tomorrow...I am beginning a documentation of the carb dis-assembly and re-assembly and I'll put pics up on my site then link them here.....

The 'hopper'
 

Grashopr

Member
Feb 22, 2002
18
0
Gaskets came in today...they are COMPLETELY wrong. Sudco's gaskets for the CRFlat carb are WAY off from our carb. I got my old gaskets to work for about an hour at practice today before they leaked again, but I am unsure as to whether I can get them to work for 2 moto's at the track on sunday. I am going to call Yamaha and chew some ass over them not supplying replacement parts for a product that they market.

The 'Hopper'
 

Grashopr

Member
Feb 22, 2002
18
0
I looked around EVERYWHERE for some sort of a liquid-gasket material that was fuel-safe...tried auto-parts stores first figuring they would have them..nothing. My local MX shop had some stuff called 1011(?). I ended up rebuilding the gaskets with it...it's grey and can be brushed on using a very small brush. The package says that once it's on, it turns into an almost rubber-like film that is solvent and low-pressure (15lbs?) safe. We'll see tomorrow whether the bike starts or not (supposed to let it set up for 24 hrs before using it).

The 'hopper'
 
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