98 jetting

[Guest Guest]

having a problem with fouling plugs.

Im thinking of rejetting to a dvp needle,180main,48 piolt jet.

My bike is yz timed air box lid removed, everything is stock outherwise.

not sure what the altitude is here in northern michigan.

[Mathew]

If you are having trouble fouling plugs - I would not recommend a 48 pilot and 180 main. Stock is 168 main with 45 pilot. I guess the needle is leaner (the straight diameter at least) though so maybe it will help. My recommendation is to switch to a CR7E plug (as long as you are not doing large sections of WOT) and be very careful when starting your bike to get the choke off quickly (10-15sec max) and not blip the throttle until it fully warms up. My feeling is that a proper heat range plug should be able to deal with a slightly rich condition without fouling (once warmed up of course). I don't feel that small jetting changes will help plug fouling much. The biggest mistake I see people make with these pumper carbs is to start revving the bike as soon as it is started. This puts an ultra rich condition (due to the accelerator pump) on a cold plug which starts it fouling. Then if the plug is slightly too cold anyway (which for moderate loads I believe an "8" is) - it will never run right again. I mostly trail ride in the woods and have not fouled a plug in 2 years (using a CR7E and being careful when starting). I pulled the plug recently and it was clean and a nice tan color.

Just my thoughts

Mathew

------------------

98 WR400F, YZ'd cam, YZ muffler

[Tim_Heslip]

Bill,

I am in the process of doing the exact thing. I have the YZ timeing, air lid removed and stock exhaust, no plug. Waiting for the needle and jets (same as you posted), I should get them in a few days. I live in the burbs of detroit. I will post my results when I get the parts and beast put back toghether. Now as soon as we get a weekend without snow...

Tim Heslip

[Guest Guest]

Thanks for the thoughts guys. I just recived my jets and needle on friday. I changed the needle to the dvp clip #3. and a 180 main.

the bike runs a lot better. the plug looks a little on the lean side. I did not change the pilot jet yet. But the bike runs so good I don't whant to change it much. maybe Ill change the main to a 182 and go from there.

98wr400

180main

dvp#3 needle

45 pilot

lid removed

by the way im runing a split fire plug.

[Taffy]

bill s

i've been telling people to use a softer plug for a year & was talking to a brick wall until before xmas.

you've asked for peoples help. one says you're richer than standard, thereby pointing out that your predicament is self induced. you then want to go even richer!!!

i've also been telling everyone here that you shouldn't look at your plug for a 'colour'. open the exhaust.

let me ask you a question then bill.

what is the correct colour of plug for a WR?

you see, there isn't one. undo your exhaust & look inside. go by feel. you'll be suprised at which colour plug makes these bikes run sweet. feel it bill.

& bill, don't run a 182 there's a good chap.

Taffy

[Guest Guest]

Good point Taffy.

I have tried going to a softerplug and it was always the same story. bike runs good a 1/4 to half all day but as soon as i WOT bingo fouled plug.I looked at old posts and the dvp

needle seems to be the ticket. I think that your right about the 182 main. if anything ill go to clip#4 on the needel. and by the way I do let the bike warm up for about 5 min

befor i hit the gas.

I also do a lot of WOT! on the fire trails up north.

[This message has been edited by bill s (edited 03-26-2001).]

[Taffy]

bill s

you're last bike obviously ran rich at low revs & very lean up top & this did for yer plug.

every bike is different. you may have the same problem with this bike.

the important thing, the vital thing is that you see the plug as a spare tyre. a "get you out the **** " fix.

while your bike is running smoothly with the new plug try taking advice off this site to LEAN & therefore crispen up the bottom end. by running the correct fuel/air everywhere you'll be able to go back to the std plug.

Taffy

[Taffy]

bill s

you're last bike obviously ran rich at low revs & very lean up top & this did for yer plug.

every bike is different. you may have the same problem with this bike.

the important thing, the vital thing is that you see the plug as a spare tyre. a "get you out the **** " fix.

while your bike is running smoothly with the new plug try taking advice off this site to LEAN & therefore crispen up the bottom end. by running the correct fuel/air everywhere you'll be able to go back to the std plug.

Taffy