All Cranked Up
Hey, I have a 2000 RM 125 and the other day the crank went out of it. I bought a crank kit and I was wondering if you could tell me how to put in my bike? I don't know how to split the cases.

Editors Note:
Umm... While are at it why don't we just teach you how to build a dirtbike from raw elements. You know - mining, smelting, refining, extruding, engineering, drafting, casting, milling, welding...

You may want to consider taking it to a shop - this is not a beginners project! The tools alone cost a small fortune.

Start with your owners manual - you should have one that came with the bike. You could also ask the prior owner for it - if applicable - or order a replacement at your nearest dealer. If you then have additional questions about how this is done - write us a note that will not require a 40,000 word answer. Neither Tuner or I have unlimited time or patience.

- Editor

Nah, William, it isn't that bad.

First pull the motor and split the cases. Next press the new rod kit in the crank halves. Now reassemble the cases. See, it's easy.

Sorry (Name Withheld). This is a major job that a lot of dealers screw up on a regular basis. Just finding someone who can correctly press a crank together can be tricky.

MX Tuner

Just to show that we all ask dumb questions sometimes...

Turbine Core II Repack ???
Dude - when I bought my Turbine Core II - I noticed that there are permanent rivets so that it cannot easily be taken apart for cleaning or a repack. Never seen this before, my old FMF Turbine Core came apart easily. Does the new design not require maintenance? Any ideas?

William Perry - Editor

Yup. Drill or grind the rivets. A lot of silencers have to have the rivets removed. Get a rivet gun (they're cheap) and reinstall new rivets.

MX Tuner

Clutch Release Arm Removal
96 Suzuki RM 125. I cracked the clutch [cover] and bought a new one, but I am having difficulty getting the clutch release arm from the old one to the new one. The owner/service manual doesn't specify. I have tried banging it out from the bottom with no luck and I am afraid to damage it. Maybe I need a special tool.

Thank you for any help,

Daniel

Virtually all of these type set up have a set screw near the top of the shaft going down to the clutch. This must be removed. In some models, the top bearing and seal must be pushed out before the shaft will be able to be removed. The only way to drive the bearing and seal out is to tap on the shaft itself. Normally, the bearing will need to be replaced.

MX Tuner

Radiator Guards
I was thinking about purchasing a radiator guard for my cr250. I was wondering if it is a good thing to have or just a waste of my money.

Thanks, Joel

There are a couple different types of guards. There are braces that mount in back of the radiator to help give it more structural strength in the event of a fall on its side. In rare instances, these can limit air flow. There is also the type which mounts in front of the radiator in place of the stock plastic louvers. These have small holes covering the front of them and can limit air flow more so than the braces that mount in back of the radiator. But these do provide the best (strongest) protection from radiator punctures from flying rocks and branches. Generally, either type can be beneficial over the stock set up as long as you don't encounter and overheating problems.

MX Tuner

CR 80 with a Disengagining Personality
Hi, I have a 1982 Honda CR-80r and when I bought it, I had to do some engine work to get it running. I had the cylinder bored out .040" and I had a new Weisco piston and ring set installed, new wrist pin and bearings, and of course a new gasket kit. Well, the bike ran like a champ for about 5 months and now I seem to be having some clutch/transmission problems. The bike has gotten hard to kick over and start, and I also noticed that when the bike is up on a bucket the rear wheel still spins when you kick it over regardless if it's in neutral or not, and regardless of if the clutch is pulled. Just before this started happening, I noticed that the clutch wasn't disengaging all the way when I stopped. My question is, what could be causing these kinds of symptoms? I know I need a new clutch, plates etc., but what might be causing the transmission to not disengage?

TJ Johnson

You need to disassemble your clutch to find out for sure. You may have broken a clutch plate and some debris is getting wedged in places that are making the transmission drag. If it is a broken plate, you?ll need to flush the transmission with fresh oil a few times to try to flush out the trash floating around in there.

MX Tuner

Revs at Start
I have a 99 cr 125 and when ever i start it, it always revs up to about 8000 rpm and sounds like it is about to blow

thanks, kc

Your low speed jetting is lean. This is not necessarily a bad thing. It sounds like your may be a bit too lean, though. You might try screwing the air screw in to the factory recommended setting first. This is usually about 1 ? turns out from fully screwed in.

MX Tuner

The RT180 Kid
I just purchased a 1995 RT180. I know its not a racer and is a small trail-bike, but, I am looking for some cheap power for it.  (Adjustments,Bolt-ons,Air Filters,etc...) Do you have any ideas?

No ideas for performance mods. You can get an aftermarket air filter but it won?t give any more power. You might be able to find some aftermarket reed petals but nobody makes any real high performance parts for your bike because of its intended purpose. You could have your cylinder ported but all that will happen is you?re going to destroy the bike riding it harder than it should be. Your RT is a great bike when used the way it was made. Riding it any harder will only get you some big repair bills.

MX Tuner

Foul Bike!
I have a problem with a 1999 yz250 fouling spark plugs after startup when the engine is cold.

The bike is completely stock. I use Yamalube 2R at 32:1 with 92 octane gas. I'm currently using a 40 pilot (stock is 50), 172 main (stock is 172), one size leaner than stock needle diameter with the clip in the top position, the air screw backed out 1.5 to 3.5 turns, and the idle adjustment (choke knob) turned fully in. This bike has a keihin pwm carb, which doesn't have an idle screw that controls the slide stop height, but instead has the idle adjustment as part of the choke circuit - you turn the choke knob out to set the idle. I've used B8EG, B8EV, and B7EV spark plugs (stock is B8EG). I live in the midwest and ride on mx tracks and trails. My skill level would be considered intermediate.

The bike starts ok - I usually use the choke on cold starts and then shut the choke off after 15 seconds and keep the bike running with the throttle. It fouls the plug anywhere from 15 sec after startup to 4 minutes after startup. It usually fouls while still in neutral or within a couple hundred feet after taking off initially as I give it more throttle. The bike sputters for a few seconds before fouling, but at that point it's too late to save it. I've tried giving it quick bursts of throttle while warming the engine up to clean it out, but this seems to cause the engine to run rough and then foul the plug. I've had the best luck letting the bike warm up at a fairly low, steady rpm for 4 minutes before even putting it in gear, and then being real gradual with the throttle after taking off for the next minute or so, but this method doesn't work every time. The other 250 riders that I've seen don't do any elaborate startup routine like this, and most that I know are using stock jetting.

I've had the bike checked at the dealer and they found nothing mechanically or electrically wrong with the bike. Yamaha said to turn the idle knob (choke) fully in, so that the bike won't idle, in order to prevent fouling, but this hasn't cured the problem either. It's never fouled a new plug right out of the box, but has fouled many on the second or third cold start. It has never fouled after starting a warm engine or in the middle of a ride.

If I check the spark plug after riding fairly hard on a mx track or on trails, the insulator is brown to black in color. If I run the bike hard through the gears a few times in an open field and then immediately check the plug, the insulator is off white in color. I thought that "cleaning" the bike out this way before parking it would prevent fouling on the next cold start, but this hasn't been effective, either. Some of the fouled plugs have been black and wet, but some have had a tan insulator, which is the desired color, I believe. I've ridden it with the next smaller main jet and still had problems with fouling, and since the spark plug insulator cleans up after high speed runs, I don't know that the problem is with the main jet. The bike runs well, and pulls smoothly from bottom to top. There is a slight hesitation down low as soon as the throttle is opened from fully closed, but I think some of that is due to the idle knob being turned fully in, which totally shuts the flow of fuel off as soon as you let off of the throttle. I'm not sure of the proper way to set the pilot jet and air screw on this particular carb, but it seems to run better with the air screw backed out at least 3 1/2 turns, even with the 38 or 40 pilot
jet.

Do you think the problem is with the jetting, or is there something wrong with how I'm starting the bike. I don't spend a lot of time at 3/4 throttle and above during normal riding, but I don't think that a lot of 250 riders do. As far as spark plug selection, I've had trouble finding B7EV's at any dealers around here, which tells me that riders are using B8's or B9's (colder plugs). Which heat range of plug would you recommend? I've used Yamaha and PJ1 filter oil with no noticeable difference. There is a little bit of black oily residue at the silencer exit, and also out of the hose that comes out of the powervalve chamber on the left side of the top end. I've ridden two-strokes exclusively all of my life, and have never fouled a plug until this bike. Do you have any suggestions on what to do?

I must say it is nice having that much info to work with. It eliminates a lot of speculation on my part and helps get you a better answer. Thanks.

When you first start the bike cold, what you're blowing out is the accumulated oil out of the crankcase. The 32:1 you're using is more than enough oil for the type riding you're doing. You can easily go to 40:1 which can help reduce this accumulated oil in the crankcase. But this will richen the fuel/air mixture. Since you're already running quite a bit leaner than stock, you should be fine with the added fuel.

I know one of the advertised benefits of the precious metal tipped spark plugs are less plug fouling but my personal experience is just the opposite. I'd run a BR7ES plug in your 250. If your local dealer doesn't have them, he can order them individually or in boxes of 10. They retail for about $2.50 so they'll save you money as well.

The one thing that is a bit puzzling is your jetting. You're much leaner than what I've found works well. A 40 pilot and the air screw at 3 ? turns out should have the thing bogging fairly significantly off idle. Personally I like to set up a Keihin carb bike with no idle like you have yours set. This allows leaner low speed jetting and enables you to get excellent low rpm throttle response.

The '99 YZ 250 had a problem with the rear pipe mount. I've seen a lot break this mounting tab off the frame. I've seen a couple that broke the silencer core due to the stress from the pipe misalignment. You'd think it would have an effect on running but it might not be that noticeable with the jetting like you have it. I'd check this by pulling the silencer apart and repack it. Make sure the core holes are clear and unobstructed.

One other thing that can cause some plug fouling is a poor electrical ground. The coil grounds through the frame tabs it mounts on. Remove the coil and sand the tabs until they are bare metal. Coat the tabs with some clean grease (to prevent corrosion). The stator grounds through backing plate. Make sure there is no corrosion in here. I'd suggest removing the flywheel and stator and putting a few dabs of grease on these mounting points as well. This can also prolong stator life.

Hope this helps.

MX Tuner

Foul Bike II!
Not long ago I bought a 1994 RM 250. The previous owner had worn out the rod and messed up the stator while racing a car on pavement (smart, I know). The bike sat in his garage in pieces for almost four years until I bought it for $600. I had the local shop put in a new rod and I rebuilt the top end and put in a new stator. The bike ran great for about the first week that I rode it with the exception of some light smoking. But after that it developed a problem, it always does the following: Runs great for a ride of any length, slow or fast, on track or trails, but after the engine cools and I start it back up it runs for about 10 seconds and fouls the plug. The plug comes out black and wet to the touch. I have tried the following to correct it:

1. Went from 172 Main to 165. 52 Pilot to 45. Needle from 3rd to 1st. 60 slide to 50 slide. With no change. (previous owner is my neighbor and ran the richer jetting without fouling so he suggested I not lean it any further)
2. Tried every plug under the sun, hotter, resistor, fancy race plugs,Etc. With no change.
3. Upon mechanics suggestion replaced right side crank seal. With no change.
4. Tried various oils and ratios. With no change.

Here are some specs on my bike:

• Pro Circuit Pipe and silencer
• Boyeson Dual Stage Reeds
• Main Jet:165 Pilot: 45 Needle:1st Float Height: 16 mm
• 92 Pump mixed with Bel Ray Si-7 Synthetic at 40:1

The bike runs very well and doesn't exhibit any problems while riding, doesn't bog or sputter at all. Starts very easily with a fresh plug or hot engine. I do turn the gas off before letting it set. It rarely fouls a plug while riding. Could you please tell me how I can diagnose my bikes problem. I would like to avoid the mechanic at the local dealer if at all possible. Any help would be greatly appreciated.

Check some of the things I suggested for the previous question.

MX Tuner

Short 'n Sweet
How do I stop the fork in my RT 100 from leaking oil?

Have your fork seals replaced.

MX Tuner

Ready for the Round file

• Year:1981
• Make:Yamaha
• Model:MX 175

I have tried my hardest to start the bike but it just won't go. I put a new .080 Wiseco in it and ever since then it has gone down hill. It got a new base gasket and I was told that using the copper head gasket could be used again, and I did. The first time I started it, it let out three blue puffs then fixed itself. It was a real rocket. Then slowly it began using plugs (I use Amsoil smokeless oil). If I put in a new one then let the bike cool after riding, it would need a new one. Then once the oil plug fell out for about three miles(transmision), and I found out, fixed it, and seemed like it made no difference. I went to start it months later it was what seemed like massively flooded, so I tried to empty the gas all out of the crankcase. I put gas into the cylinder through the spark plug hole, and it fired once and stopped. So I emptied the gas it and put in new gas and put on a new head gasket(copper) and now the carb won't put any gas into the cylinder. It just keeps on dripping out of the carb vent tubes and pretty fast too. I can't understand why it won't work. I put a new plug in, and gas into the cylinder through the spark plug hole (not too much) and it won't even fire once. What the hell can it be?

Your carb float needle is stuck open. This is dumping too much fuel into the engine flooding it. Replacing the float needle and seat is the first place to start.

MX Tuner

1999 KTM 250 MXC
Problem - None, yet. I came into some money a year back and at the ripe ol' age of 18. I wanted the biggest baddest bike in the shop and my brain told me the bigger the price tag the bigger the fun. So, I ended up selecting a used 99' KTM 250 MXC. The previous owner was the owner of the shop that I purchased it from and he told me that he had performed around $1,000 worth of modifications to the bike. Myself being new the the KTM product line have no idea what has and hasn't been replaced and what has and has not worn out. What I need is a service manual. Not the wimpy one that comes with the bike, I mean like a total breakdown of the bike with all the stock item numbers and specs. Does such a text / website exist? I also need a total breakdown of the mantainence routine for the whole bike, including suspension, engine, and electrical. Any help would be greatly appreciated!

Jesse Hawkins

You should be able to order an excellent manual from KTM. Try the KTM dealer. He should be able to get you all the literature you need for proper upkeep and maintenance.

MX Tuner

Partial Message - Vintage Restoration
I am going to restore one of these old beauties. I was wondering if you could suggest a place where I can get any of the original plastics or good quality copies. I haven't begun to tear it down yet, so I'm not sure what it will need mechanically. I'm guessing it will at least need a top end job and suspension work. I have been away from the sport of moto-x and trail riding since 1993 and I'm not sure what is still available. Any suggestions would be greatly appreciated.

Thanks

Chris
Cannonsburg Pa.

Seems we?ve lost a bit of your question. Ain?t technology wonderful? Let?s see?. For restoring most any "old beauty", Vintage Iron in Fresno, California is one of the best sources for hard to find parts. They have built some of the most beautiful restorations I?ve seen. This does come at a price, but what doesn?t?

MX Tuner

Diagrams?
hi, I have a 1982 Suzuki RM 80 and I need a diagram and a picture on how to put it to together. If you could send me those it would be greatly appreciated!!

Thanks, Matthew

Your Suzuki dealer should be able to get the proper manual for your bike. If they no longer have them available, a Haynes manual may be your next best bet. Your dealer should be able to get a Haynes manual also.

MX Tuner

Power Valve Adjustment
i just bought my first bike a 94 rm 125 ,how do you adjust the power valve?

There is a small cover on the left side of the cylinder (as you?re sitting on the bike). The cover is held on by two small screws. And has a round opening in the middle. Loosening the two screws will allow you to turn the slotted round part in the middle. This adjustment is for the power valve return spring. Turning this slotted cover clockwise will increase the tension on the spring holding the valve shut. This makes the valve open at a higher rpm. Soooo?. Turning the slotted cover ccw will loosen the tension on the spring making the power valve open at a lower rpm. Move the cover in ? turn increments.

MX Tuner

Inseam Challenged
My brother and I are 5' 4" tall, we are both interested in buying new 2001 dirtbikes. The problem we are facing is that when I sit on a new YZ,RM,CR etc. 250 I can not seem to touch the ground. I currently have a 1984 YZ250 with the big slope coming from the gastank to the seat, I can touch the ground pretty good but not flat footed on both sides, but Im able to stop and start the bike. It seems that on the newer model bikes that we can not touch the ground. I know that releasing the tension on the rear spring will make the rear suspension bouncy but it still does not squat the new bikes low enough, The funny thing is that the new model dirtbikes 125s seem to be taller that the 250s as much as a 1" on some models, I quess what Im looking for is a combination of suspension parts that will lower the newer bikes, CR250 as well as make the bike compettative for racing without sacraficing an extreme. If you could help my brother and I would be greatful.

By far the best way to handle this is to have the suspension lowered. You can have it lowered by as much as you want. You?ll need to do both ends equally to prevent any handling problems from arising. I?d try to find a suspension shop that is familiar with this mod. I know Jeremy at MX Tech has done many of these. He?ll do it 100% correctly. Try www.mx-tech.com for more info. He can go over the pros and cons of having it done and can go over how far to have it shortened. It isn?t cheap but the overall results are phenomenal for someone who is "inseam challenged". Depending on how far you get it shortened can affect the costs involved. Jeremy can go over all this with you.

MX Tuner

Jet Set?
my son has a 1996 kx 80.we are installing an fmf rev pipe/ powercore II silencer, boyesen reeds, and a vertex piston.

my question is what jet sizes would you recomend.

Nobody can accurately recommend the specific jet sizes since there are many variables that affect jetting. Weather conditions can, and will, have a significant bearing on what jetting you come up with. The correct thing to do is install all your parts and then rejet. Learning how to do this will reap you major benefits now and in the future. Eric Gorr has an excellent section on his website concerning jetting. Go to www.eric-gorr.com for more info.

MX Tuner

Piston Slap
Mark, I just bought a 1994 XR250 from a guy who was apparently afraid to change oil. It smokes some when it gets warmed up, and the piston is slapping (buzzing) a bit when it gets ridden hard. I am assuming a ring job is in order. I called the guy that sold the bike to see what had been done to the motor. He said "slight over bore and a bigger piston". Should I start by mapping all of the cylinder dimensions, and then find piston and rings to match? Or should I check the gaps and replace parts as needed?

Thanks - Bob

I?d pull the top end down and have the bore measured. Depending on how much it is worn will determine what the next sized piston needed will be. Make sure you find a reputable shop to do this measurement.

MX Tuner

Mid to Top End Performance
Hello I purchased a 1994 cr250 I love the bike. My problem is It doesnt seem to have as much power as it should.The motor was completly rebuilt (thanks to a hole in the case from a snapped chain) I did new trans bearings new mains and seals new pivot rods and governer for the power valve ,new boyesen reeds and new vertex piston.The bike has stock jetting and a dyno port pipe with a stock silencer.I have rode my friends 96 rm250 and anothers 95 yz250 and both bikes seem to have alot more mid to top power.My bike does great lowend wise.I can usually pull 2nd gear in tight turns where they are both in 1st.I guess if you can suggest anything it would be greatly appreciated. Thanks Brian

Sounds like your power valve isn?t opening. The linkage where the cylinder fits down on the cases can be a bit tricky to get right. There is a round cover on the left side of the cylinder. This will expose the end of the power valve. You?ll see an H and an L next to the cover. The end of the power valve has a slot in it. With the cover removed, start the motor. When you rev the motor, you should be able to see the slot rotate from the L to the H as the power valve opens. If the valve isn?t rotating, this is your problem. It may be as easy as reinstalling the cylinder correctly so the power valve linkage is engaged properly.

MX Tuner

WR250F Performance Mods?
I purchased a 2001 YAM WR250F. I had read the article on the 400 that y'all put out and was wondering if the same specs for the modifications were close to the same.

I want to keep up with my son, he rides a 125YZ. HELP!

Danny Parlington

The exhaust cam timing can be altered exactly like the 400/426 to obtain YZ timing specs. Unrestricting the exhaust and removing the throttle stop and air box snorkel should get you going in the right direction.

MX Tuner

Cluth Slipin?
I have an 89 Cr80. I just had a new shaft and shifter put in, and i had the  oil pan plug redone. Befor that the motor ran fast and strong and even for the first maybe 10 min after i got it from the shop it had power. Then all of a sudden it feels like its slippin when i hit powerband almost like the gears are slippin. Im in the process of selling this bike so i dont want to go into changing a lot of things to try and see what te problem is. I know the guy that re did the shifter would have noticed if the gears were stripped or worn and would have said something. Im thinkin either reeds or rings but is it also possible my cluth could of suddenly started slipin or maybe the mechanic put thick oil in it or something. I would greatly apreciate any advise

It seems you?re describing the clutch slipping. I?d check to see if the clutch has any free play in the cable. Either that or the bolts that hold the clutch springs in are backing out. IF that?s the case, it won?t be long until the hit the inside of the side cover and make a big mess of things.

MX Tuner