1997 Suzuki rm250 running rough

[Ripntear1922]

So i just bought a 1997 suzuki rm250.  The guy i bought it from said that the previous owner just did a complete engine rebuild.   It will start and run, but runs rough with not alot of top end power.  It also will not idle. I believe its running rich so i cranked the idle screw in all the way in and the air screw 2 turns out,  i got it to idle for about 1 minute this way and then tryed adjusting the idle screw out a couple turns and it died again.  I still have to dig into the carb and check float level and make sure everything is up to snuff.  My biggest worry is the top end power not being there, just kinda sputters in 1st and 2nd,  i was able to get it to hit the powerband for a quick second in 3rd gear a couple times but nothing regularly.  Any advice would be greatly appreciated!!! 

[The Spanky]

You need to start with the basics. 

Don't just assume a rebuild was done unless you have proof. Check the compression. 

Have you changed the plug?

Is the fuel fresh?

What condition are the reeds in?

Remove the carb and thoroughly clean it. Make sure all the little air passages are clean and the float height is set to spec. Verify what brass is in the carb, and do a search on here for what jetting specs people commonly run on that bike to give you a reference point. 

[OLHILLBILLY]

"The guy I bought it from said the previous owner did a complete engine rebuild". That pretty much says it all.. ?

Get ready to tear it down and do another complete engine rebuild like the one that the previous owner of the guy you bought it from did back in 1999.. ?

Edited July 4, 2018 by OLHILLBILLY

[Ripntear1922]

Haha.   Thats what i was thinking too.   You never know.   So he did say that the previous owner added a ton of oil to the first tank of gas and he hadnt run it through fully,  so i drained the gas this morning, didnt drain the carb..... Put a 32:1 mixture in it and went on my property to try to run the old gas out of the carb.     Pretty quickly after that i was getting alot more power on the top end and is running much better!!  Still not perfect but i feel better about my purchase already .    I still havent torn down the carb but just got this bike yesterday.  About 20 minutes after it started running better i did a plug chop and im running lean.   Still wont idle but deffinetly not as rough as at all levels of rpm now.   He must have put massive amounts of oil in the gas to make it run so shitty.      So my next step is still to take carb off, clean everything up.  I did notice the carb is leaking slighty out of the float tube, so i probly will need a new needle and seat, or at least adjust the float. Also there is a pro circuit silencer but a stock header, and the header has about 4 dents in it.   Would a dented header affect the performance?

[Ripntear1922]

Ok so just got into taking the carb off and checking the air filter.    The air filter is really bad.  The carb i took apart and cleaned everything with carb clean.   Took the float cover off and found the float has no spring at all to it and is sitting all the way down on the needle when i turn it upside down.   This is my first 250 ive owned.  This is not right correct?  My sons kawasaki kx 60 i had to replace needle and seat and when i turn the carb upside down it wouldnt engage the needle, i would have to give it a little pressure and then it would bounce back up.  They should both work the same way correct?

[Ripntear1922]

[The Spanky]

Yes, the float needle should have a spring. 

Those small dents in the pipe that I can see in the picture will have very minimal effects. 

Thoroughly clean or replace the filter. You'll never diagnose a running issue with a dirty filter. 

I will never understand why people "add extra oil" after a rebuild. It's pointless and stupid. 

Now that you're getting a picture of how poorly maintained this bike was, it should indicate to you that you need to thoroughly go over everything. Clean and grease the linkage bearings, headset bearings, wheel bearings. Go over all the spokes and every nut and bolt. Church the reeds. Service the forks and shock. 

And I would put a top-end in it.

[Ripntear1922]

Thanks for all the advice!  Im gonna order a new filter and a carb rebuild kit for now,   gonna buy a compression tester as me and my family are just getting into riding.  So i noticed that 1 spoke on the rear tire is missing, and the front forks have a little oil on them.    How crucial is that spoke and is the oil on the front forks normal?  Also i bent the tange on the float so the float would sit level with the carb case and now gas piurs out of the float overlow tube.   This tells me the needle and seat need replaced correct?  Thank you again spanky for all the input!  I really appreciate it!

[Ripntear1922]

It has v force 3 reeds in it.   Have not checked them for damage yet.

[The Spanky]

37 minutes ago, Ripntear1922 said:

Thanks for all the advice!  Im gonna order a new filter and a carb rebuild kit for now,   gonna buy a compression tester as me and my family are just getting into riding.  So i noticed that 1 spoke on the rear tire is missing, and the front forks have a little oil on them.    How crucial is that spoke and is the oil on the front forks normal?  Also i bent the tange on the float so the float would sit level with the carb case and now gas piurs out of the float overlow tube.   This tells me the needle and seat need replaced correct?  Thank you again spanky for all the input!  I really appreciate it!

The oil on the forks means the seals are leaking. It's an easy fix if you have the knowledge and the right tools, but most likely the bushings are worn and the oil needs changing anyway, so just have them serviced. It will only be a couple hundred plus parts. Do the shock as well. If you have the money to spend, have the suspension properly set up for your weight, skill and riding conditions at the same time,  you'll thank yourself for it every time you get on the bike. Properly set up suspension will improve your comfort, control and speed more than all other modifications put together wil do. 

You will never get the float setting correct if the spring is missing from the seat. And even if it wasn't missing, level with the carb body isn't correct. Typically they will be something like 7-9mm above the edge of the carb body, when holding the float so that the needle barely makes contact. This gives the spring the range it needs to keep the needle seated when the bowl is full even when the bike is bouncing around. 

The missing spoke isn't an issue if you aren't flat landing big jumps. But my OCD would never allow me to leave that on my bike lol. But I'm sure you need to true the wheels and check the tension on all the spokes. 

Edited July 4, 2018 by The Spanky

[hondaxr650rrrr]

While you are in the carb replace the float, as yours is 20yrs old. They are not too expensive. Check and make sure the powervalve is working properly and not gummed up, especially with the PO love of 2 stroke oil.

[Ripntear1922]

Ok so just ordered a carb rebuild kit, and air filter,  gonna start with that to see what it does and then do the carb spraying around the gaskets to see if i have an air leak anywhere.    Then go from there.    My local shop told me about 200$ for the forks to be serviced, just like you said spanky.   I was also thinking to check the powervalve.  Im gonna start with the carb and the air leak testing and see what i come up with then make the decision to rip into the engine or not depending on how she runs. 

[The Spanky]

1 hour ago, Ripntear1922 said:

Ok so just ordered a carb rebuild kit, and air filter,  gonna start with that to see what it does and then do the carb spraying around the gaskets to see if i have an air leak anywhere.    Then go from there.    My local shop told me about 200$ for the forks to be serviced, just like you said spanky.   I was also thinking to check the powervalve.  Im gonna start with the carb and the air leak testing and see what i come up with then make the decision to rip into the engine or not depending on how she runs. 

Be aware that $200 is only for the labor. Parts and oil will be in addition to that. They can't give you a total until they get them apart and see what parts need replacing. But if it's just seals, bushings and oil, it shouldn't be more than $400ish.

Edited July 5, 2018 by The Spanky

[Ripntear1922]

Ok so just got the carb rebuilt.   Replaced all the brass and the needle.   The seat is not replacable...    so got everything installed and new air filter,  went out and ran it with air screw at 1 1/2 turns out and idler at 2 out.     I have basically all my topend power, at least i think so,  front tire pulls off the ground in 2nd through the powerband.  But i still have no idle and its boggy at low rpms....    i sprayed a generous amount of carb clean on all the gaskets of the engine and both the carb boots and reed..   no fluctuations as far as i can tell.   Basically just kept it idleing smooth with a steady touch of the throttle and nothing changed......im gonna check compression tomorrow "have to go buy a tester"....     any other thoughts on this???  I read a forum from a 92 rm250 that he had to cut some of the choke boot down so the choke was seated all the way in the carb.....    think this is a possibility?

[The Spanky]

Now that you have everything in good condition,  it's time to go through this:

 

Spanky's Jetting 101: 

A correctly jetted carb makes a tremendous difference in the torque, midrange pull, top-end pull, and over-rev of your engine. If you have never jetted your bike correctly, you will almost certainly gain some performance at some point in the bike's powerband. 

A cleanly jetted pilot circuit can be the difference between having to clutch the bike out of a turn or not. Hard starting when hot or cold, poor response when opening the throttle, reluctance to idle, all of these are symptoms of an improperly sized pilot jet or incorrectly adjusted air screw. 

The needle can make all the difference in the world for the power of the machine in most situations, as it controls the throttle range that most riders spend most of their time using.

A correctly sized main jet could mean the difference between being able to rev out high enough to not have to shift one more time at the end of the straight, or the power falling flat on top and requiring you to make that extra shift. 

Are you fouling plugs? Many people will tell you all sorts of band-aid fixes, from running less oil, to running a hotter plug. Both are incorrect fixes for plug fouling. It's all in the jetting. An engine that is jetted too rich will have combustion temperatures that are too low to burn the fuel and oil effectively, leading to deposits and wet fouling of the plugs. 

Do you have spooge? There are the rare instances where a mechanical issue, such as a leaking wet-side crank seal, can cause spooge. But, by and large, this isn’t the case. In most instances, spooge is caused by rich jetting. It has nothing to do with how much oil you mix in the gas, or how hard you ride. An engine that is jetted too rich will have combustion temperatures that are too low to burn the fuel and oil effectively, resulting in deposits, plug fouling, and spooge. Spooge is nothing more than unburned fuel and oil entering the exhaust. 

The only way to know what jetting changes you will need is by trial-and-error. No one can give you jetting specs, because every bike is different, every rider has a different style, and jetting is totally weather dependent. Unless the person telling you what jets to use is riding an identical bike, on the exact same track, at the same time, his recommendations are meaningless. Someone with a good understanding of jetting can get you in the ball park, but you need to do the testing to determine the correct jetting yourself if you want it right. 

Jetting is fairly simple, and is a useful skill to learn if you ride a two-stroke and want it to perform at it's best. 

It's very important that you start with the pilot circuit, because the pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving. 

Before you start to re-jet your bike, you need a clean air filter, a fresh plug (actually you need several plugs to do plug-chop tests for the main jet), and fresh fuel. 

One important detail: Make sure the engine is in good mechanical condition. If your engine has a worn top-end, fix it first. Trying to jet a worn out engine is a waste of time. The same goes for reeds that don't seal properly, and a silencer that needs re-packing. Worn reeds will mimic rich jetting, and worn rings will mimic lean jetting. 

Before you start the jet testing, Install a fresh plug. Set the float level to the proper specs, an incorrect float height will affect your jetting all across the throttle range. 

All jet testing must be done with the engine at full operating temperature. 

As already stated, start with the pilot circuit. Turn the air screw all the way in, then turn it out 1.5 turns to start. Start the engine, and turn the idle screw in until you get a slightly fast idle, or hold the throttle just barely cracked, to keep the engine idling. Turn the air screw slowly in, and then out, until you find the point where the idle is fastest. Stop there. Do not open the screw any farther, or your throttle response will be flat and mushy, and the bike may even bog. This is only the starting point, we will still have to tune the air screw for the best response. 

Now is the time to determine if you have the correct pilot installed in your carb. The air screw position determines this for you, making it very simple. If your air screw is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet. If your engine doesn’t respond to air screw changes, then you either have a dirty carb, or the pilot jet is way too rich. When the pilot jet is way too rich, you are forced to use the idle screw to open the slide so far in order to keep the engine running that the pilot circuit is partially bypassed, and the engine is actually starting to draw fuel through the needle jet. 

Once you have determined (and installed it if it's necessary to change it) the correct pilot jet size, and tuned the air screw for the fastest idle, it's time to tune the air screw for the best throttle response. Again, make sure the bike is at full operating temperature. Set the idle back down (the bike should still idle, despite what you read in the Moto Tabloids), and ride the bike, using closed-to-1/4 throttle transitions. Turn the air screw slightly in either direction until you find the point that gives you the best response when cracking the throttle open. Most bikes are sensitive to changes as small as 1/8 of a turn. 

The air screw is not a set-it-and-leave-it adjustment. You have to constantly re-adjust the air screw to compensate for changing outdoor temps and humidity. An air screw setting that is perfect in the cool morning air will likely be too rich in the heat of the mid-day. 

Now, it's time to work on the needle. Mark the throttle grip at 1/4 and 3/4 openings. Ride the bike between these two marks. If the bike bogs for a second before responding to throttle, lower the clip (raising the needle) a notch at a time until the engine picks up smoothly. If the bike sputters or sounds rough when giving it throttle, raise the clip (lowering the needle) until it runs cleanly. There isn't really any way to test the needle other than by feel, but it's usually quite obvious when it's right or wrong. A too-rich needle can often be felt simply when revving the bike on the stand. The bike will sound rough and raspy when blipping the throttle on the stand. A correctly jetted bike should rev cleanly and crisply.

Last is the main jet. The main jet affects from 1/2 to full throttle. The easiest way to test it is to do a throttle-chop test. With the bike fully warmed up, find a long straight, and install a fresh plug. Start the engine, and do a full-throttle run down the straight, through all gears. As soon as the bike tops out, pull the clutch in, and kill the engine, coasting to a stop. Remove the plug, and look deep down inside the threads, at the base of the insulator. If it is white or gray, the main is too lean. If it is dark brown or black, the main is too rich. The correct color is a medium-dark mocha brown or tan. 

Please note that, when reading plugs, the tip of the insulator, threads, etc. are meaningless for jetting purposes. They can tell you a lot of things, but jetting isn’t one of them. Only the mixture ring at the very base of the insulator, inside the threads, can tell you anything about the jetting. 

This should help you read plugs:

The slide is also a tuning variable for jetting, affecting the throttle range from 1/8 throttle to approximately 1/3 throttle. If you can’t clean up the small-throttle jetting on your bike no matter how lean you go with the pilot or the needle, the slide is the next step. But few bikes need leaner slides. 

Keep in mind, even though this article is intended primarily for two-strokes, four-strokes also need proper jetting to perform right, although they are not quite as fussy as their oil-burning cousins. The only real difference in the two is with the pilot circuit. 

Two-strokes have an air screw that you screw in to make the jetting richer, and screw out to make the jetting leaner. Four-strokes, on the other hand, have a fuel adjustment screw that you screw in to make the jetting leaner, and out to make it richer. Their purpose is the same, they just do it in different ways.

[Ripntear1922]

Thank you for this!!!     I will deffinetly look into the jetting!!   Also i havent  checked the reeds yet.    They are vforce3 reeds but havent looked at them. And how do i know when i need to repack the silencer?    Man im a newb at this but trying to learn!!  Sorry for all the questions.   Sending a pick along.   Is this one of the jets i replaced with the rebuild kit?

[Ripntear1922]

Ok so i started it up today with the idle screw all the way in and the air screw at 1.5 turns.     I got it to idle that way until it warmed up.  I beleive thats telling me i need a bigger jet as im running lean.     So what is in there now is a 172 and a 48.     Which one should i change or both, and how much bigger should i go?    I also started it up last night when it was 70 degrees or so and it idled for a little while.  But still sputters in low rpms and dont want to drive it much when its running lean....  

[The Spanky]

9 minutes ago, Ripntear1922 said:

Ok so i started it up today with the idle screw all the way in and the air screw at 1.5 turns.     I got it to idle that way until it warmed up.  I beleive thats telling me i need a bigger jet as im running lean.     So what is in there now is a 172 and a 48.     Which one should i change or both, and how much bigger should i go?    I also started it up last night when it was 70 degrees or so and it idled for a little while.  But still sputters in low rpms and dont want to drive it much when its running lean....  

You need to read the above guide, and follow it in order. To clean up the idle you have to focus on the pilot circuit, forget about the main jet for now. 

You will probably want to go to a 45 pilot jet though...

One thing at a time.  ?

Edited July 7, 2018 by The Spanky

[Ripntear1922]

Ok so turning the idle screw all the way in is the only way way i can get it to idle at all (only when its cold)   the air screw doesnt really change the idle at all even all the way in or basicslly all the way out.  Just repacked my silencer last night it was super nasty and havent started it up yet this morning.    I didnt change this out as the other one looked like it was in good shape.    Should i change it out anyway?

[Ripntear1922]

Ok just did my compression test,  i read after that i was supposed to dhut the gas off and run it till it died..    i didnt do that so sont know if it will screw my numbers up but i was at 120 psi....    im thinking thats kinda low.   Ill do some research to dee what its suppised to be at