250r question

[gsxr68]

I just got my motor back together and it has a skip in the upper rpm in the higher gears. The head has been cut and so has the cylinder they are both stock. The carb is stock also with 155 main jet. Sparks MX pipe and silencer. It did not do this before the rebuild but has not run in almost 2 years. I put in 110 fuel with a br8eg plug. I really want to get it running right like i said it has been almost 2 yares and do not want to wait any longer. Thanks

[deathman53]

go richer on the main, go to a 165 or 170 to start

[JTRtrx250r]

if the head/cyl been cut, you might need to regap your plug, try 0.018, also be sure the petcock flows freely

Good luck to ya!

[Tom TRX250R]

I agree with Deathman53. Definately jump up the main jet to a least 170 or 175. I'm running 175 in mine and I started at 180 and did plug chops from there to achieve perfect jetting! :D

[gsxr68]

OK got it to pull through to full throttle. new plug 175 main. Now I do not know if this is typical 2 stroke or not but a steady throttle it is not smooth it feels like it is missing. Is this the way they act with a steady throttle or do I need to work on something else
TomTRX250r wrote plug chops please explain what that is and the right way to jet.
Thanks

[deathman53]

that might be too rich

[Tom TRX250R]

It all depends on the motor. I know two friends that have their R's identically set up motor wise and we're all running different jets. All motors aren't the same considering jetting. 175 might be too large just depending on your altitude but 175 is perfect for me. Plug chop basically means to buy several sizes of jets and experiment with each one. Put a new plug in and run at about 5 min. getting up to full throttle several times. After that pull the plug out and see which color it is. That should tell you exactly what jet you need. Remember it is better to run a little on the rich side than too lean!!!! It will hestiate for a second but won't burn your piston up!!!

[deathman53]

I usually run my bike a bit rich too. It makes them run cooler also, just alittle bit, but its something. I have a 250r trike, so my jetting is gonna be a bit different than a quad, as the frame of the trike is a air passage way as well as under the fenders(I don't use a airbox lid). I am currently running a 182, dpp needle(I think) 1st notch, with the pilot jet the 38 a/s includes, this on a ported cylinder, v-force reeds, esr atc 5 pipe and silencer. don't forget your needle plays a part in jetting too, do you have the stock carb? try getting a richer needle.

[wilkin250r]

A "plug chop" is a way of reading your jetting off your spark plug.

Basically, you start your bike, warm it up and all that good stuff. Make sure it is truly warmed up. I usually take mine out and ride it around for ten minutes or so.

Now you're ready for a plug chop. Find a long straight, preferably close to your house. Ride your quad along that straight, in any gear you choose, and hold the throttle at a certain position and don't move it for several seconds. Let's say the throttle position you are interested in is full throttle.

So, right now, you should be riding this long straightaway at WOT for at least ten seconds. Now, as quickly as possible, hit the kill switch and pull in your clutch at the same time. This is the "chop". You're killing your motor dead. Do NOT let it return to idle, do NOT let off the throttle. Kill the motor, pull the clutch, and let it coast in neutral (or, you can apply the brakes, but only AFTER the motor is dead)

Your spark plug will now tell you EXACTLY what was going on inside your motor at WOT. Do a search (both here and on the web) for spark plug reading and what it tells you.

WOT plug chop will tell you your main jet size.

1/4, 1/2, and 3/4 throttle plug chops will all tell you your needle taper and your clip position.

Idle plug chop will tell you your pilot jet size and air screw settings.

It's very important that you chop your engine quickly. Your spark plug can only tell you what was just happening in your engine. So if you run at WOT for thirty seconds, then let off the throttle and let it drop to idle before you kill the engine, your spark plug will tell you what was happening at idle, not at WOT.

[gsxr68]

Thanks guys was looking foward to jetting and riding but the plastic piece for the choke broke on the stock carb so I ordered a 38 airstriker carb today. No need in spending the time since I am going to replace it. Thanks for all the info, will put it to use when I get the new carb. Could the carb be the reason for the engine not running smooth with a steady throttle. Is the airstriker a good choice.

Thanks again

[Roostin250R]

Yes the airstryker is an excellent choice, however it may be a little to big if your motor is pretty much stock, if you plan to do more modding to the motor in the future, then you should go ahead and get it. If not, a 36mm would be a better choice depending on your intended use. You might lose a little off the bottom as your motor stands now with the 38. IMO the stock carbs work pretty good but with them getting as old as they are, you are better off just replacing it. I run a 38 airstryker on mine, and its worlds better than stock.

[wilkin250r]

Originally posted by gsxr68
Could the carb be the reason for the engine not running smooth with a steady throttle.

It could be several different reasons, but the most likely is the carb. It could also be an air leak, bad compression, spark, or fuel-related.