Need a little tuning help '96 RM250

SoFlo · Jan 8, 2006

Well, it's a few things really. If I leave the gas in the float bowl when the bike is stored, over the week lets say, it will be next to impossible to kick start it, you basically HAVE to pull it, and it take like 10 seconds sometimes to get it going at 10 or 15 mph. If I empty the bowl before storing, I can start it preety easy next time. What's the deal with all that, normal?

Second, is plug fouling and jetting. I'm using BR8ES plugs, and they last less than an hour, lately. I've started using this Belray sythetic stuff, and it's fouled alot more than the motul synthetic I used to have. The fouling by oil.
Lets say I have it pinned in 4th down a dirt road, then I slow down, 1/4 throttle in 1st, and then I pin it and start moving out again, that will almost always cause the plug to die right on the spot. Seems that after I go from steady high revving, to a steady low, and back up to crazy, it'll foul.
It won't foul if I'm trail riding with alot of throttle variation and clutching though. But it were to slow down, then nail the gas again, that could do it right there. And when you start it up, it seems to load up preety quick, unless you had previously shut it off right after aggresive riding.
I've got the needle on the 2nd from top clip, 165 main, and a 52 pilot. Again, BR8ESs getting oil fouled.
And one last thing, when it's got a brand new plug, it revs and runs fine, maybe it's just slightly rich somewhere causing the fouling. I was hoping the fast, slow, fast thing would uncover a certain jet problem.

2-Strokes 4-ever · Jan 8, 2006

First thing I'd looking into is float height, or maybe the float is stuck (flooding carb) Make sure there's no dirt/varnish up in the main jet (won't let float close to shut off fuel flow) Don't know what the stock main jet is, don't think your 165 is so far off that it would cause those symptoms. Look for dirt/varnish first.

SoFlo · Jan 8, 2006

I hear that some people put the float so that it is like parallel with the bottom of the carb, or straight sideways, you know.
Or do I adjust it to 16mm like the manual says? I've cleaned out the carb a bunch of times, but the float bowl could very well be the problem.

2-Strokes 4-ever · Jan 8, 2006

Make sure float is set to manual's specs. (at 45 degree angle as to not let spring tensioner compress) And check to make sure valve seat (where fuel comes in) is not crudded-up.

SoFlo · Jan 9, 2006

Another thing that I have just remembered is that I had a preety good leak coming out of the pipe to cylinder joint, it was seeping out, and even slightly squirting onto the pipe in front of (after it curves to the left, and then back across to the right, that part). So it was a preety bad leak. With the leak and the jetting I had, a plug would last for 1 full day. With the leak fully patched up, it's down to an hour. I'm guessing it richened up the misture without the leak, so I think I'll go like 2 down on the main, and maybe one down on the pilot and see what it does? Is that too big a change?

MXer · Jan 9, 2006

I have a 96rm250 I run a BR7ES. This is a hotter plug. It works very well for me.

mazuniga · Jan 9, 2006

I think it may be too big pilot jet, try changing to a 45 and see what happens. You can go down to an 40 with no problems. In the main jet department can go to 155 with no risk at all.
The needle should be second groove from the top.

SoFlo · Jan 9, 2006

Exactly the info I was looking for, those minimum #'s. The only thing that I'm afraid of with jetting is going to lean and causing a meltdown. I'll try dropping down to those sizes, check the plug, feel for hesitation too. If that doesn't work, I'll jet back up a little and try a hotter plug. Great info and thanks everyone. Additional tips welcome.

berno11 · Jan 9, 2006

I had that exact problem with fouling.
My mainjet and needle were worn and letting too much fuel through. Check that next

rodH · Jan 10, 2006

have you checked the powervalve and powervalve linkage? I started fouling plug on every ride on my 97, turns out this was the problem, I have gone months on hte same plug now.

sick 96 250 · Jan 11, 2006

when i had my 96 it had basically the exact problem and i used the fmfracing.com tech jetting center as a starting point for jetting and went from there. As for the floats i beleive it was 16mm to measure

I beleive i ended up with a 52 or 53 pilot and a 168 main with the needle on the 3rd clip. Also make sure your top end is straight and has correct compression, mine had good compression but it was scored some from running lean so once it was changed out i had no more problems with throttle response or fouling of the plugs. Your pilot seems good, maybe the top is to rich causing it to foul when you go wide open then close it down then back to wide open. I had many threads regarding my 96 and jetting problems if you just wanna search for them.

SoFlo · Jan 11, 2006

sick 96 250 said:
when i had my 96 it had basically the exact problem and i used the fmfracing.com tech jetting center as a starting point for jetting and went from there. As for the floats i beleive it was 16mm to measure

I beleive i ended up with a 52 or 53 pilot and a 168 main with the needle on the 3rd clip. Also make sure your top end is straight and has correct compression, mine had good compression but it was scored some from running lean so once it was changed out i had no more problems with throttle response or fouling of the plugs. Your pilot seems good, maybe the top is to rich causing it to foul when you go wide open then close it down then back to wide open. I had many threads regarding my 96 and jetting problems if you just wanna search for them.

Alright, I'll search and see what was in those threads. About the powervalve, I don't think it would have anything to do with it in this case. The bike has great lowend and topend, and it runs fine. Just think of it this way, for that 1 minute that it has a brand new plug, the throttle response is very snappy, it revs great and clean, great power, it just runs perfect. Then within the hour, I feel the bogging come and then it's done.
I think that when I sealed up that massive leak I had with the engine to pipe connection, it richened up the jetting to the point where it just fouls every hour, then again, with a fresh plug in it, the bike doesn't run rich in my newbie opinion. Never bogs, and the tire will throw roost the second you nail the gas.

Either way, I'm going to adjust the floats to 16mm, drop the main from the 165 to a 160, drop the pilot one down to a 50, and go from there. If that doesn't work, I'll go back to 165 and 52, and try a one hotter level plug and see what happens. If none of that works, I'll go back to the BR8, then start checking reeds, the topend, silencer packing, and the powervalve. I'm going to ride this Saturday with the leaner jetting, and maybe with the hotter plug, and report on what happens.

And the open, closed, open combo is exactly what fouls the plug after it's been used for a while. Also, the needle is at the second clip, I'll probably just leave it there for now. And the compression was checked like 30 hours ago, it came in at like 185 pounds, but like you said, the compression isn't the whole story. I bought this bike used a few months ago, and the floats were set to not let any gas in, the needle was at the richest setting, with a 178 main in, and it even had a lawn mower spark plug to boot. So I don't know where this bike's been or what kook has owned it, but soon, all will be right! :boss:

sick 96 250 · Jan 11, 2006

good stuff, jeep us posted, if i remember correctly once i put a new top end in my bike i had well over 200psi, maybe like 225? It could be just the top end is worn although it still hauls. When mine was giving me problems, once it was started up it ran great but wouldnt idle for crap, ended up being way to lean and it scored the piston just enough that when i got the jetting situated i needed a new piston for it to run correctly. You can grab em up on the famous auction site for like $20 then 2hrs of your time and your good. I would still put the needle on the 3rd clip anyways why your doing everything else to the carb, only takes 5 sec and then go from there. Good Luck man :cool:

SoFlo · Jan 12, 2006

On allthingsmoto they are telling me to buy a new needle and seat, because it's letting gas into the carb and stuff, and that's why I can't start the bike if I leave the petcock on and gas in the bowl.
Is that just the little plunger that the floats move? Or are they talking about the main needle, with the clips on it? I'll keep the thread updated when I start adjusting things. I'll test it out this Saturday hopefully.

sick 96 250 · Jan 12, 2006

a new needle and seat is possible if it is worn, but def check the jetting and i would also inspect the top end. Just pull the head off and see what the piston looks like, if its all carboned up or not. The seat is the little rubber piece in the carb that closes off the gas when the floats raise up, if it is rounded off at the tip it could cause some problems as what you are describing but i'm guessing it is more the jetting and piston. If you pull the head and its really carboned up try to sand it off a little and use carb cleaner to clean it. here is a pic of what my piston looked like when i needed a new one although i had good compression.....

sick 96 250 · Jan 16, 2006

any updates??

SoFlo · Jan 16, 2006

Yes and no, the stupid dealer of course doesn't carry any jets, and still haven't gotten them in. I did try running some BR7ES plugs, but they were only slightly better than the 8's. It doesn't matter if I run it hard or easy it seems, it'll foul in about 30 to 40 minutes. Mostly just oil fouled, it carboned fouled once out of the 5 or 6 times, I rode for a good 5 hours I think on Saturday. Tommorow I think I might pull the head and take a look. Might as well check the reeds too, and a leak down test.
When I rode a Blaster, this is the way the jetting went, you put in a new plug, and rode at a certain RPM range for like 2 minutes straight, then shut it off, pull the plug, and see what's what. I assume that works for dirtbikes too right?

sick 96 250 · Jan 16, 2006

here are a few threads of mine that may help ya out..... past problems on mine and a friends RM...

http://www.dirtrider.net/forums3/showthread.php?t=105135

http://www.dirtrider.net/forums3/showthread.php?t=100598

http://www.dirtrider.net/forums3/showthread.php?t=100838

Maybe this can help a little

And to check the plug, use the search function and search for plug chop or plug check, etc. Should be a ton of info on the correct way to do it.

SoFlo · Jan 17, 2006

Reading through those 3 threads, it's like a nightmare, like there's 40 different things it could be! What are just the first basic things that I should check? Quick, simple, and cheap things first, harder and more expensive things later is how I want to do it.
What order should I do all this in,
Pull the head and invesitigate
Check the reeds
Compression check (Before pulling the head?)
Leakdown test (Checks both left and right seal that way)
Look through the carb (Do they sell Keihin rebuild kits with floats, the needle and seat, etc?)
Clean airfilter and fresh silencer packing would be a good idea
Set float level (Preety sure it's 16mm right?)

First things I should do is just clean the carb, are there rebuild kits for it?
I'll check the reeds
I need the freeze plug thing for the exaust, and I need a bigger intake plug.
I think the silencer could use some fresh packing too, and as always, a clean airfilter.
I should be checking back in here today.

sick 96 250 · Jan 17, 2006

first clean the airfilter and see if it helps, then i would check compression, although it can be misleading but still check it, pull the carb, head and inspect them and the reeds as well. You should be able to find the stuff you need for the carb at any moto shop. Do a good cleaning of the carb again, i wouldnt do a leakdown test just yet but possibly if everything else fails. I'm betting you just need a new top end and a good cleaning of the carb, filter, and a silencer repack.

Are there any other dealers around you? You dont have to go to just a zuki dealer for the jets, other dealers carry same brand and stuff as well just make sure its the same brand and type, bring a jet with you when you go

SoFlo · Jan 17, 2006

Nah, I was ordering the jets from a regular motorcycle shop. Of the 3 or 4 shops that are in the area, non of them stock jets. When I've asked if they do, they answer no, like why would you even think we would?!

SoFlo · Jan 17, 2006

I'm going to do a leak down first before anything, just so that I can save a couple of gaskets. I'm hoping to have the bigger intake plug that I need by the end of the week. If that checks out good, than it's all coming off! :boss:
sick96250, what is your email address, or aim screen name, so that I can keep you updated, and just let this thread sink down. You're a good help man, thanks.

sick 96 250 · Jan 17, 2006

just hit me up on IM anytime, i work a decent amount but at night i'm mostly home, i believe you IM'd me the other day but i X'd it out before i relized who it was. Just click the lil IM tab in the post and you should be set

As for pulling the head, just empty the rad fluid threw the drain hole, undo the nuts on top and you should be able to get a decent view of the top of the piston. To put it back on, put the O-rings that seal it up in the freezer for a lil and you should have no trouble getting them to fit back in, you dont have to pull the whole head off just yet, at least you can get an idea of how the piston looks

Need a little tuning help '96 RM250

SoFlo

2-Strokes 4-ever

SoFlo

2-Strokes 4-ever

SoFlo

MXer

mazuniga

SoFlo

berno11

rodH

sick 96 250

SoFlo

sick 96 250

SoFlo

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