Author Topic: Jetting suggestions for my 86 R (Read 6818 times)

nick20555 · « **on:** May 31, 2016, 10:38:48 AM »

I decided to stick with my stock carb for a little bit longer and I'm gonna need some help with a starting point for jetting. I just bought this 86 trx250r so I am not 100% on the the parts it has. I do know that it has a curtis sparks exhaust but I'm unsure of the which of the sparks exhausts it is. Maybe I can get pictures up for you guys to maybe identify it. I just put a new uni filter on it. I will be running the outerwears cover for a lid and haven't decided if I want to block the stock snorkel or not yet. Guy said it has motor work done but is unsure what. He does know that it was bored .030 over and I can see its the stock cylinder. He also said it must run 93 octane so I'm thinking something has been done to the head for that reason. Other than those things listed, I don't really know the details on what else is done yet. I am at 400' elevation and ride in temps from about 40-90 degrees. It currently is in the low 80s right now. Any ideas on a starting point for jets? Just from what I have read I was thinking starting at 160 on the main and plug chopping to see how close that is and maybe middle clip on the needle and the stock 48 pilot or maybe a 50. What do you guys think though, you would know better than me where to start.

This is all I got for pictures of the pipe. It isn't in the best shape right now. I might send it off the get cleaned up and fix the best they can do if it is the sparks mx because I hear that is an excellent pipe.

rablack21 · « **Reply #1 on:** May 31, 2016, 12:14:28 PM »

If it's a sparks pipe, It should have the letters "mx" or "tt" stamped into the name plate. As far as the jetting, so you are running a stock 34mm PJ carb; is that correct? I would start out with the richest main jet you have, around 175ish or so if you have it. Then work your way down with plug chops. Plus, if the top end is super lazy and flat feeling, then you know you are way rich. As far as the pilot, I would say start with a 45 or so and go up. If it is real "zingy" and doesn't want to idle down, then you know it is too lean. Go up until it settles easily. I doubt anything has been done to the head. It is pretty common for everyone to run 93 pump gas if they are not running race fuel.

nick20555 · « **Reply #2 on:** May 31, 2016, 01:00:43 PM »

I'll have to check again but I don't remember it being stamped with the tt or mx just the sparks plate on the side. Yes I will be running the stock pj 34. I just saw a lot of people running in the high 150s for mains with the sparks exhaust of the jetting sticky. Same thing with high 40s on the pilots as well. I think right now it has a 152 and 48 pilot but when I got it, it had a filthy filter, exhaust was cracked, carb bowl was cracked and had 2 gaskets stacked up on each other and the clip was bent on the needle so no idea where that was supposed to be. I knew when I got it that it wasn't riding right but still had some power. I'm glad I saw this when I did so I didn't run it lean and blow it up. The guy I bought it from rode it and acted like that was normal but I knew something was off. I got a new bowl and rebuild kit in my cart on jets r us as well as a 160 main. I'll probably add a 170 to it and call it a good start for now.

If you are asking about the phrase plug chop, I learned that on blasterforum since I have a pretty nice blaster as well that I built. Its when you get the quad warm, put a brand new plug in, then go through the gearbox WOT for about 15-20 seconds, then pull your clutch in and kill the motor, take your plug out that you did the WOT pull with and chop the threads off so you can see the color of the smoke ring left. If your smoke ring is barely visible then you are too lean and if the smoke ring is a nice cardboard color but not too dark then you're perfect. Obviously, if its really dark then you are super rich. That's obviously only the process to check your main jet. They suggested something similar for the needle with the only change being that you do a 1/2 throttle pull instead of WOT. Blaster throttles had a spot for a throttle stop screw so you could set that at 1/2 for your 1/2 throttle plug chop real easy. These are methods that they suggested to people who don't have the experience to tell purely off of the feel and sound of the quad. Since I only have experience with blasters and the Rs are a different animal then I will probably do this to get a good start on my jetting.

rablack21 · « **Reply #3 on:** May 31, 2016, 01:08:58 PM »

Oops. Sorry. I wasn't questioning the plug chops. Just a grammatical error.lol. My bad.

nick20555 · « **Reply #4 on:** May 31, 2016, 08:40:23 PM »

I found out why it didn't have a tt or mx stamped on it; it's because it's a bill's pipe lol. I don't know why I thought it was a sparks

rablack21 · « **Reply #5 on:** May 31, 2016, 09:14:16 PM »

I didn't think it was, but I was giving you the benefit. Lol

RIDE-RED 350r · « **Reply #6 on:** May 31, 2016, 09:23:00 PM »

Just looked in my Honda service manual. Stock jetting specs for '86 was #145 main and #42 pilot. Sounds like you are running a near stock cylinder with exhaust. I'd start 2 sizes richer than stock specs on each, that should keep you safely rich. I would bet that it will settle in the mid 150's on the main and 45 or so on the pilot. I wouldn't be a bit surprised of the pilot jet in it now is too rich at 48. Just a guess here, but was it real blubbery and lacking in power down low till it "cleaned out" as you gained RPM during acceleration?

I get it if you opt to start out richer at 170 and 48 though. Nothing wrong with playing it safe.

Skeans1 · « **Reply #7 on:** May 31, 2016, 09:57:44 PM »

Quote from: rablack21;67972

I didn't think it was, but I was giving you the benefit. Lol

They did some early stamped pipes that weren't labeled as well Ryan.

nick20555 · « **Reply #8 on:** May 31, 2016, 09:58:20 PM »

Service manual I downloaded says that 86 had a 150 main and 48 pilot

Aceman · « **Reply #9 on:** June 01, 2016, 12:37:47 AM »

I think trying a 48 pilot, maybe 1.5" turns out on the air screw, clip on the needle in the middle and a 160 main jet isn't a bad place to start.

nick20555 · « **Reply #10 on:** June 01, 2016, 09:27:06 AM »

Quote from: Aceman;67976

I think trying a 48 pilot, maybe 1.5" turns out on the air screw, clip on the needle in the middle and a 160 main jet isn't a bad place to start.

That's what I was thinking. Parts are already on the way. We will see soon enough. I'll report back when I get working on it. Might be a little bit since I will be out of town 5-13th. Hopefully I can at least get it started before then so I can order parts before I leave and have them when I get back.

RIDE-RED 350r · « **Reply #11 on:** June 01, 2016, 05:55:31 PM »

Quote from: nick20555;67975

Service manual I downloaded says that 86 had a 150 main and 48 pilot

Hmm, that's interesting. My Honda service manual is for the ATC's and that was the spec listed for the '86. I wonder if there was a change after my manual was published.. Either way, I think you will be plenty safe at 160 and 48.

I would recommend getting an assortment of jet sizes for both main and pilot jets. Yeah, at 6 bucks a piece it adds up but you'll be glad you did.

Skeans1 · « **Reply #12 on:** June 01, 2016, 08:55:20 PM »

Quote from: RIDE-RED 350r;67997

Hmm, that's interesting. My Honda service manual is for the ATC's and that was the spec listed for the '86. I wonder if there was a change after my manual was published.. Either way, I think you will be plenty safe at 160 and 48.

I would recommend getting an assortment of jet sizes for both main and pilot jets. Yeah, at 6 bucks a piece it adds up but you'll be glad you did.

Good option would be buy one of Eddie Sanders jet wrenches with the jets.