Almost there on jetting, need more advice

Today I went from the following:

DVR #3

172 main

48 pilot

2 1/2 out.

Many thought this was waaaayyy to rich for the Denver Altitude (5500 - 9000). But it was running.

I put in what the jetting guys recommended:

EKQ #3

165 main

45 pilot

2 out (Kouba in, great tool as you all know).

After I got it started (more on that at the end) it seemed to run like a bat out of hell. Damn near flipped it over. No hesitation at all anywhere through the powerband (but that was just up and down the street). You guys are geniuses!

Two problems though, 1 minor, 2 possibly major.

1) Minor backfiring as the bike became warmed up. Not even sure if it is a problem.

2) Very hard to start! It would only fire over with the hot start button out and no choke. Now with my old jetting I had to have both the hot start and choke pulled out to start it up. I now neither scenario is correct but as I said the bike ran.

Since I have the jetting closer to what is recommended and it seems to have made a difference. I would like to figure out why it is so hard to start.

Any ideas on why it only starts with the hot start button? After it fires up, I push the hot start back in while giving it gas to keep it running. Then I pulled the choke out and let off the gas and it warmed up just fine.

It just will not start with the choke out right off the bat. I am perplexed.

As a side note, I do have the idle all the way in (slide lifted). Always had to do this since I went to YZ timing two years ago.

Thanks guys. Doug

Correct me if I'm wrong but doesn't the choke richen the mixture? If so then if it won't start with the choke on that would mean the pilot jet is too rich. Right?

Try giveing thumper racing a call (1-800-259-5186)

Tell them the bike you have and any mods you have

done and the elevation you are riding at.

I did and they told me exactly what i needed to do

It was fool proof.

They will also sell you what you need.

Good luck DRZ AL!

yeh go buy it from the experts they'll take your money.

wait a minute, **** you do the opposite to what you're advised to do- i nearly forgot!

so, er! now let's see if i can get you there; whatever you do keep that needle. and whatever you do definately pay the dealer to set your bike up. whatever you do don't change the needle to the one every other idiot advised you to get. keep the one you've got.

the problem you've got is that you haven't turned your bike around before trying to start it. so always don't turn your bike around. next you should kick it in trainers coz you gotta feel that bike. finally did you heat up the floatbowl with a ronson lighter.



You have a 400, right? No lid, aftermarket or uncorked exhaust?

At your altitude a 42 pilot may work better. 2 turns out on the idle mix is on the rich side also.

I think the reason it was so hard for you to start is because you have radically changed the jetting. I changed my pal’s WR 426 jetting, pilot, needle, and main, and promised him it would now run better but that he may have a hard time getting it started until he became accustomed to it. I was right on both counts.

It is also possible you had flooded the bike with the choke and needed the hot start out to get it to light.

Anyway, if I were you I would set your idle mix first. Warm the bike up thoroughly and turn your idle down very low and go in a ¼ turn on the fuel screw. If the revs pick up a little, try another ¼. If it continues to run better at less than one turn out that could be indicative of an overly rich pilot.

So next you could try a 42 pilot and see if it ran better like that. Just ignore whatever the bike is doing until it warms up. If it backfires while you are warming it up then don’t ride it until it will idle without the choke at its normal idle speed setting. If it backfires after it is warm try and determine the approximate RPM and throttle position and we can fix it, i.e. ~ 5k + and closed throttle popping on an otherwise good running bike is easily fixed by going smaller on the pilot air jet. Did you put a YZ sized PAJ on your WR? Up there you may be better off with the WR size, or better yet buy a PAJ screw so you can set it exactly.

Finally, next time you go to fire it up be disciplined about it. Pull in the release and kick it through (no throttle) a few times before you try it. If it doesn’t threaten to light after three or four kicks turn up the idle one turn (over normal idle speed). Still no luck then prime it slightly (quick half turn of the throttle) and try again. If it doesn’t threaten to light after three or four kicks clear it out (throttle open, release pulled, five good kicks should do it) to make sure you haven’t flooded it. Then start over, this time with the choke. No luck, clear it again, and turn up the idle some more.

That drill will start just about any four stroke (that does run). If at any point it tries to start but dies, or even just pops, you know you are heading in the right direction, and clearing out the engine allows you to get accurate feed back on what you are doing, instead of whatever it was you were doing ten kicks ago.

Hope this helps.

Thanks Hick, I'll give it a try next time I have her out. I was definately happy with performance up and down the street. It wanted to come off the ground in 1st through 4th gears. WOW!

I'll take it to a track and spend the day tweaken it.

Taffy, you been down at the pup all night tossin pints? What the hell are you talking about? :)

Dougie, sounds like your getting close with the jetting. I got the EKQ needle last week from Vicery but haven't had time to install it yet. Keep posting any other changes/results you make. I'll let you know the same with mine.

I'll give the 42 a try guys. I have not touched the PAJ. Since I still have the "octopus" on, I didn't touch the air jets. They are still stock.

I also didn't do the Taffy mod yet. I got the 3/32" RC wheel collars that Damon suggested but they were just a bit too small. I'll try the next size up. He is right though, they do look like they were machined for this purpose.

I also found out that I was missing the spring and O ring off the fuel screw. I took it out and I thought "shouldn't there be a spring on this". I looked it up on the 'fische and sure enough, missing the spring and O ring. Of course you just can't buy the spring. $28 for a new fuel screw set. Of course Vickery had it in stock. Best parts dept. around.

Not sure when I will get to tinker again. Might be awhile. We are going up to Grand Lake on Thursday for a long weekend of snowmobiling. Get to try out that new Arctic Cat 900 FE. My butt's puckered already :D

Keep me posted on your results Kerry. I'm anxious to see if you get the same performance increase. Try the 42 first :)

Larry, we are talking about changing our Moab trip to April or early May. Let me know when you plan on going. Maybe we can book the same weekend.


Had the same problem when I started playing around with a 45 pilot jet. Ended up back on the 42PJ/75PAJ and it starts first kick cold (with the choke on). I believe my fuel screw is set at about 1 - 1.5 turns out as well.

I think the 45PJ/75PAJ that you have is way too rich...

Next step (once this freekin' snow melts again!) is to go down to a 40PJ...and then a 38PJ...making the corresponding PAJ changes as see what Taffy's getting at.

For now though, make the 42PJ change...and you'll be very happy!

FYI...went to Watkins on Sat...before the snows came. It was like riding on asphalt...very hard stuff. They definitely need to do a bit of grading out there. Everyone in the world was out there as well! Fancy 70 degree day and the track's super busy. Given all of that, it reminded me of just how lucky we are to have Rampart Range a short distance away. Riding on the track sucks and gets boring in a hurry...


[ February 25, 2002: Message edited by: LarryCO ]


Have fun amigo! I couldnt imagine being on that 900...Jim's 800 is way too much power for me...

Sounds good on the Moab deal. We'll be out there soon. I'll keep you posted...

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