Author Topic: Newbie Jetting Questions (Read 1817 times)

HectorTheHut · « **on:** January 25, 2013, 10:29:40 pm »

Can anyone point me in the right direction as far as jetting? Stock carb, FMF pipe, VForce reeds, and a clamp-on UNI filter and a 20cc dome running on 110 at sea level. Can anyone ballpark me on jetting? I just re-did the top end with @ a fresh 69mm bore. I've kinda been half-assed heat cycling it, but I don't want to screw anything up before I run it hard. Any info would be greatly appreciatred.

LT250RWV · « **Reply #1 on:** January 26, 2013, 05:01:11 am »

Im running 40 pilot and 200 main on stock carb.I have boysen rad valve fmf and silencer ,kn filter,Head shaved .20.bored 69mm with some porting.Im at 2000 above sea level and ride up to 4,300 feet also the temp has been way below 30.What is your temp and sea level i might be able to help you out a little better to get you in a safe ball bark so you can get it right.

HectorTheHut · « **Reply #2 on:** January 26, 2013, 09:40:36 am »

I'm at sea level and generally ride from 60-70.

GrkGuy · « **Reply #3 on:** January 26, 2013, 02:36:58 pm »

send iceracer a pm, or ask him a question in the tech section on here

Iceracer · « **Reply #4 on:** January 26, 2013, 04:56:57 pm »

Read and follow. The open filter may want a couple sizes richer main TO START.
http://www.suzukiquadracerhq.com/bartlett-racing/jetting-1007/

HectorTheHut · « **Reply #5 on:** January 26, 2013, 09:41:26 pm »

The legend replies! Thanks a lot man!

Alright so I'm running a 270 main right now, which according to a jetting guide I used to jet my Banshee is okay. But the pilot jet is a 30. I ordered a 280 main and a 35 and 40 pilot. I was running a 30. Good thing I only heat cycled it because that's lean as hell.

LT250RWV · « **Reply #6 on:** January 27, 2013, 12:48:09 pm »

I would try a 40 pilot then go from their.Im not sure on your top.I put a Scp pipe with a 270 and was way to rich.With the fmf on i only run a 200 With the Scp ! was was running 230 with it.In summer i ride A 35 pilot and 195 main on stock carb.The 40 im running now is too rich but it hasnt been above 22 degrees for the week.Im going back to 35 today.Its above 40 today and in the 60 for the next 3 days.Also have you done a leak down test to make sure you dont have any leaks.

GrkGuy · « **Reply #7 on:** January 27, 2013, 01:52:56 pm »

for doing the heat cycles its better to be rich than lean, if you can wait to finish the heat cycles till you get the other jets

HectorTheHut · « **Reply #8 on:** February 02, 2013, 01:20:44 pm »

Okay I finally got my jetting pretty much dialed in. I think what threw was that I was under the assumption that this bike was running lean because before I bought it, my buddy scuffed the piston whilst at the dunes.

Anyhow, now I'm running a 250 main with a 35 pilot and a stock jet needle with the clip in the second position from the top. That last bit threw me, but ended up being the key to my jetting woes.

HectorTheHut · « **Reply #9 on:** February 06, 2013, 07:58:37 pm »

Just posting this in case it helps anyone else: run a damn leakdown test!

So I thought I had it all dialed in and it was good to ride, I took it out to the desert for some slow riding.

Warmed it up, smoked a bit much, but revved up fine. After taking it for a quick short spin, it started to misfire--like a fouled spark plug.

Pulled the plug wonder wtf was the matter, and it was covered in black liquid. I thought there was no way in hell I jetted it rich. Had my buddy pull me back to his truck and then I noticed a similar looking black liquid all over the front of the motor coming from where the pipe mates with the exhaust flange.

Finally, I broke down and made a leakdown tester for it and ran the test. Bad oil seal. Explains why the guy I bought it from fried it and explains the oil fouled plugs and exhaust leaking. Could have saved myself a lot of banging my head against the wall (and countless 12 packs of beer.)

Quadracer250r · « **Reply #10 on:** February 07, 2013, 06:03:36 am »

could you tell me the stock size of 90 quadracer 250 carb?

HectorTheHut · « **Reply #11 on:** February 07, 2013, 05:34:46 pm »

It's a 34mm Mikuni TM34SS. Uses 4/042 main jets, VM22/210 pilots, of which, according to my service manual are (stock) 260 and 30 respectively. Don't know the needle taper off the top of my head, but the clip should be in the 3rd position (stock.)

LT250RWV · « **Reply #12 on:** February 10, 2013, 03:27:34 am »

stock jetting is 240 main 45 pilot, on the 87 to 92,lt250r

LT250RWV · « **Reply #13 on:** February 10, 2013, 03:30:41 am »

Im glad you didnt blow it up from the seal.Leak down test is the only way to go after major engine work.

Andys92 · « **Reply #14 on:** February 10, 2013, 05:50:52 am »

reading my clymers now. stock jetting for 88 and up :pilot jet 37.5, main jet:240. needle clip 3rd groove ,needle #6fp63 and air screw is 2 turns out . The 1985 was the only model with a 32mm carb. .The 86 is the only model with the vm34ss mikuni that had 45 pilot (according to my manual).Not sure how this differs from the jetting you are using right now .
Now i have a question , judging by others "stock jetting" answers ,
how can manuals differ so much !??

LT250RWV · « **Reply #15 on:** February 10, 2013, 11:56:45 am »

Quote from: Andys92 on February 10, 2013, 05:50:52 am

reading my clymers now. stock jetting for 88 and up :pilot jet 37.5, main jet:240. needle clip 3rd groove ,needle #6fp63 and air screw is 2 turns out . The 1985 was the only model with a 32mm carb. .The 86 is the only model with the vm34ss mikuni that had 45 pilot (according to my manual).Not sure how this differs from the jetting you are using right now .
Now i have a question , judging by others "stock jetting" answers ,
how can manuals differ so much !??

I just checked my Clymer too.Say the same thing as your does..Both my quad came with 45 in them when i bought them.The one was bone stock. The ome parts look up call for model f/g 45 which is 85/86 model h 37.5 which is 87 models /j/k/l/m/n/ uses 30 pilot which are 88/89/90/91/92 ,This info is off ome parts look up they use at local Suzuki Shops.

HectorTheHut · « **Reply #16 on:** February 12, 2013, 06:32:10 pm »

I can't find the half sizes of the needle jets anywhere. I can find the ones for my Banshee, which are similar but shorter, but not for the LT.

Also, the seals seemed to solve one problem, but I'm still having a lot of trouble with the bike. Can't figure it out.

LT250RWV · « **Reply #17 on:** February 14, 2013, 12:57:53 am »

What is it doing

HectorTheHut · « **Reply #18 on:** February 14, 2013, 08:18:37 pm »

Well, after I put the seals in and reassembled the engine covers, I went to start her up. After a few kicks it started and seemed like it was going to run fine. I let it idle for a while and it smoked a ton less than it had before. After it was good and warm, I took it for a spin down the block. Everything was going great until all of a sudden it started to bog really bad. I gave it some gas too keep it alive and after a second it bogged down again and died. After that I couldn't get it started for the rest of the night.

The next day it started right up, and then promptly died again. It did this a couple times until it just wouldn't start at all. Think it was possibly a timing issue (due to a nasty occasional kickback and backfiring), I checked out the woodruff key which looked fine. The only thing I can think of is maybe a bad ground. The spark plug looked good and I put a new one in for good measure. If anyone can point me in some direction, any direction, it would be greatly appreciated.

LT250RWV · « **Reply #19 on:** February 16, 2013, 12:18:55 pm »

Didnt you rejet it before you found the airleak. Since you had the airleak im sure you jetted it super rich to fix the lean condition of the air leak.Also when you done your leak done test how fast did it leak off preasure,.Blog off sound rich to me.when it wouldnt start did you try a new plug in it to see if it would start. Sound like you fouled the plug to me.

HectorTheHut · « **Reply #20 on:** February 18, 2013, 06:50:15 pm »

Spark plug looked fine. I'm thinking either my reeds are shot, or I have a bad ground.

LT250RWV · « **Reply #21 on:** February 19, 2013, 07:57:15 am »

Keep us updated on it

HectorTheHut · « **Reply #22 on:** February 23, 2013, 06:11:37 pm »

I think I got it! Finally dammit!!!!

Okay, so all this time I was looking at the less-likely solutions to my problem. First I thought it was jetting, bad seals (I did have a seal I had to change--but it wasn't causing the majority of my problems), bad reeds, and a shorn woodruff key. And I'll be damned if Occam's Razor didn't apply here. This whole time, it was an electrical issue.

First off, the symptoms all pointed to a fouled spark plug, but my pigheaded ass thought there was no way. Every time I pulled the plug, it looked good. I didn't even check how well it sparked because the bike WOULD fire up. So today I get a wild hare up my ass and decide to check the spark. It was weak and wouldn't spark half the time, but the spark plug itself looked totally good. I even tried it with a new one, same thing. This caused me to check the wiring and clean up the grounds as well as the part where the magneto passes by the magnet. I did all this, and the spark improved a ton, but it still didn't look right to me.

I couldn't figure it out, I was ready to give up when, for the hell of it, I deced to use a b8es spark plug off my Banshee. Sure as ****, that thing gave me a nice fat blue spark. The whole time I was using one of those stupid ass "Type R" resistor spark plugs. I had a similar issue with those with my Banshee (certain years didn't require them and the resistor plugs weakened the 'Shee's already weak spark). So there it was--a twenty three year old electrical system coupled with a resistor spark plug makes for a poorly running bike. The most simple explanation was it.

So now that that problem is out of the way, I'm still looking to dial this thing in. So the FMF website says I should be running a 240 main, 30 pilot, and needle clip in the third position. I'm assuming the FMF settings assume that the bike has no other modifications. If that's the case, how should I jet for the FMF pipe in addition to clamp-on UNI filter (no airbox) and VF2's at STP?

LT250RWV · « **Reply #23 on:** February 23, 2013, 07:09:12 pm »

I was ruuning my fmf setup 200 main 35 pilots needle 4th clip.I had boyshen rad valve,kn filter,Head shaved .20 trail portting.I was fat on my main a bit, when its warmer i ran 195 main.It ran really well on that setup.But before i done the porting and shaved head it was the same jetting i used before and after the mods.

HectorTheHut · « **Reply #24 on:** February 24, 2013, 12:44:08 am »

91-92 jetting is different than 88-90 jetting I believe

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Author Topic: Newbie Jetting Questions (Read 1817 times)

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