Don’t Ask: Dirt Bike Technical Q&A

Aug. 08, 2011 By Rick Sieman
If you choose to email a question to this forum, then you must conduct yourself accordingly. Therefore, the following rules are in order:

1. Do not write your email to me IN CAPS. If you do so, I will print out your question and do terrible things to it.

2. Do not request a personal e-mail response. Since I get thousands of questions each month, trying to answer them all would cut deeply into my leisure time, which I value more than your current state of confusion.

3. Try to spell at least in a semi-correct fashion. If you choose to mangle the English language, expect no mercy from this quarter. You might be mocked severely.

4. Do not ask for me to send you copies of my many manuals and literature. I am not in the library business, nor do I want to spend the bulk of my day at the copy machine just because you're too lazy to ask your dealer,  or look around a bit.

5. Don't bother me with truly stupid questions, like how to get 50 more horsepower for a buck and a half

6. Now that you know the rules, think carefully and have at it!
Oh yes … I’ll leave your e-mail unedited, for what it’s worth.

Hello Rick,
Please give some advice. I have been searching the web for 3 days now and can't seem to find the solution or the true problem I am having with my 89 Honda NX 250. So here is the symptoms. Turn the key on, lights work, horn works, all power seems fine. however when trying to start the bike the starter only spins (at what seems to be a normal rate). the only thing is that it sounds like its just free spinning. I'm not so confident inside a motor but i have removed the starter case to reveal the gear that connects to the gear/gears inside the motor. these gear/gears i would think to be more difficult to spin by hand since when turned is/are supposed to turn the motor over.
I must confess i let a self called experienced rider take her out in a field one day. as this no named person proceeded to travel away from me i noticed the experience must have came from a video game. Uh, tree, in a field. key word field. well what happened to the tree seemed worse than what happened to the bike since the gear shifter didn't actually become severed instead it bent back to the foot peg. i limped her home and she ran and started fine for about a day. then came that free spinning sound of terrible confusion. please help me. i could send you video, pics, sounds, anything that may help you help me. thank you for taking the time to read my issues.
Will Bailey

Chances are that the sprags (gears) on the backside of the starter are badly moved out of position via the impact of the bike on the tree. Your best bet is to remove the starter and see if the area that attached to it can spin freely, or if it has normal resistance. That should be a clue as to whether it received internal damage or not.

By the way, the NX 250 was an interesting little bike by Honda, a crossover dual-sport motorcycle available in the USA from 1988 through 1990. It is a lightweight bike intended for both on-road and off-road riding. It was never produced by Honda in substantial numbers, but it was met with generally positive reviews with its perfect balance of power, size, and style.

It was only available in two colors, Metallic Blue and Pearl White. In some countries Honda continued production of the NX250 up to 1993. It was named "Dominator" and came in various other colors.
Other Don't Ask Columns:

July 2011

June 2011

May 2011

yamaha L2515970, can you tell me anything about this bike thanks

Your e-mail is typical of the kind of stuff I normally would throw away, but for some reason I decided to see if I could find out what you really have. According to the numbers that I was able to look up, you probably have a 1967 YL2-C (I think Yamaha called it a Trailmaster) 100cc rotary valve trail bike ... in this era the L2 is the product code and the next six digits are the serial number ... in 66 there were only five digits in the serial number (with L2 prefix).
You ought to consider yourself very lucky that I didn't print out your e-mail and do terrible things to it. However, I will mock you severely with my various knowledgeable friends. Let this be a warning to you.
By the way, I was able to determine what kind of bike you have by contacting Keith Lynas, the man who owns OSSA PLANET ( and is also quite possibly one of the smartest men on the subject of vintage bikes. And you better not have a stupid question for him, as he has no tolerance for stupidity.
Live in Colombia SA.-
How can I get user and mechanical manuals from Honda CBZ motorcycle 160cc, 2005 model, preferably in Spanish?

Aristides Sourdis Movilla

Your best bet, my friend, is to get one of the free translation programs available on the Internet. Several of them are quite good and easy to use. It makes a lot more sense to use these rather than to search for manuals in Spanish. While you can find manuals in Spanish, you're only going to find a few popular brands and manuals on Spanish made bikes.
Re: Big Bore Kits for 2006-07 Kawasaki KLX 250
what about the cylinder head and bigger cams????
juan restrepo

Don't bother trying to hop up the KLX motors. I rode one that a friend of mine had spent several thousand dollars on to make it competitive, and I quite easily blew it off with an old 1990 KDX 200. As you can tell, I've never been a fan of that particular model and have always felt that it was underpowered, unreliable, heavy and an outdated design that didn't respond to normal hop up procedures. Sorry if I sugarcoated it.

I'm trying to rebuild my marzocchi 50mm forks but i can´t find the brushing anywhere.

Where do you buy yours from?

Ahhh, yes  … You seem to bre searching for brushings? I'm not qruite srure where you can frind brushings brut you might start with arny dealer who hrandles brikes writh Marzocchi forks. And don't tell them we sent you.
Re: Yamaha Vintage Dirt Bike ID Guide
trying to find out if my bike is a mx 360 and year of make vin no is rt1-186121 thanks

This is a much more confusing question than it would originally seem. A great number of the RT1 bikes throughout the Yamaha model run were actually identified by RT2, even though they were RT1s.  Your bike, as far as we can figure, is a 1972 RT2 MX 360.
Dear Rick,
I'm having a little trouble with the shifting on my 1979 125 Maico. It keeps hitting neutral when I go to shift from 1st to 2nd gear. I can't seem to get it to go all the way in to 2nd no matter how far I move the lever. From what I've gathered, Maico, for reasons unknown, decided to use the DKW/Sachs shifting mechanism, which would explain alot. But I have been unable to find anything on how to adjust the mechanism so that it hits 2nd gear correctly. Any thoughts?

While the Maico motor was a dazzling power plant, the gearbox was less than wonderful. The motor used in the motocrosser was also used in a Maico road racer of that era and was competitively fast. The fact that Maico chose to use the gear selector from Sachs should tell you everything you need to know as to why it doesn't shift worth a tinker's damn. The terrible thing was that once you've got the transmission adjust to work okay, a half-hour later it started missing gears again, especially the shift from first to second. I have heard of racers who have put a Koba shift kit in their bikes modified for the Maico gears, but I have not done one myself. Lots of luck with this one.
Yup. Me again. I was looking at the old "Don't Ask" pages. Remember some dude on the 10/9/09 D.A. who pulled his plug wire on his runaway Hunkavarnish and got a new hairstyle? I have a similar one, though I didn't get shocked. I was given my fellow TT500  riding friend's '68 Taco 99 mini bike, by him. I told him I would get it up and running since it was laying in his back yard about 1/3rd. of the way into the ground. This was about 1986.
I took it to work. Removed the cylinder head to look inside the 13 cu. inch (206c.c.)  Briggs flathead engine to check condition. As long as the head was off, I milled it by doing figure 8's on the shop floor with it. White Trash Bros. Performance Engine Works.  Put on new chains and different gearing/sprockets to account for the 125 pound weight gain since the last time I rode it in 1970. New countershaft bearings, too.  Cleaned tank/carb, etc. Didn't hook up throttle. Thought I would fire it up and just work throttle by hand.
Keep in mind the first thing Dave did when his folks bought him this in '68 was disconnect the gov and pitch the muffler, screwing in a pipe-straight. I'm at work (Simi U-Rent, First Street, just down from Billy Payne's Payne Engineering)  The crew is all standing there watching this historical event. I shot a bit of gas into the carb, yank the cord and fffaaaazzzZZZZOOOOOOOOOOMMMMMMM!!!!!  RUNAWAY W.F.O. ENGINE!
I have a death-grip on the bars. It launches forward and STRAIGHT UP, the front tire inches from the ceiling! Gravity takes over. Back down it comes. Rear tire hits shop floor again and launches straight up again! It went through this cycle about a dozen times. I'm screaming at the top of my lungs for one of the idiots to "GRAB IT NEXT TIME IT COMES DOWN!" At 55,000 r.p.m. they can't hear a thing. Besides, their jaws are on the floor. I'm starting to laugh so f***ing hard I'm about to lose my grip on the bars. Finally, I grab the frame with my knees when it hit the floor and managed to pull the choke.
After recovering, I asked the stoops why they didn't HELP ME!  One idiot goes, "We thought you were doing it on purpose!" Yeah, next I'll endo on purpose!  Rick, you know you can't make this stuff up. Maybe the r.p.m. was a bit of a lie, but, hell, when this kinda thing is happening, who KNOWS how fast that little bugger is revving out!
Still got the bike. Still starts first pull on original engine. Got a kill switch on it and a carb. return spring off my garage door. I think I told you this story before, but I enjoy telling it so much. 
Here's a shocking story: It's about 1967. My older brother and I traded 2 slot cars and $7 for Roger Mortenson's go-cart. (he later went on to race class 1 buggies-blowing his engine every race) The cart had a 2 h.p. engine, direct belt drive and solid tires. A FINE unit. 0 to 6 in 15 minutes, stuff like that. I was hauling ass down our street in 1000 Oaks and saw some friends up ahead.
I thought I would be cool and reach back to push the ground tab against the spark plug and coast up all cool. Well, I didn't look back while I did it and laid my right wrist right on top of the bare plug. Ever have someone grab all your veins, tendons and muscles in your wrist with a pair of vise grips and try to rip them out? That's what it felt like. At ANY rate, it DID kill it and I DID coast up to them. One goes, "Hey, man! What happened to your hair?" I tried to explain the extreme top speed of this fine unit wrecked havoc on the hair. I think they bought it. Later.  
Dave Fruhling
Once again, we are running Dave's stories as if they were an absolute truth. We don't know this to be a fact, but here they are, for what they're worth. Sit back and enjoy them.
An old family friend passed away a few years ago and I was given a lot of his stuff, including a bunch of Mechanics Illistrated Magazines. You know, the rag with automotive's version of Super Hunky...Tom McCahill. One from the late '60's had an article on how to improve the performance of your dirt bike. The bike they used as a test-bed was a beautiful new Harley-Davidson Baja 100. You know, the one. To quote you when you tested it in D.B. magazine "...a rehashed Italian streetbike with no redeeming values." (or something like that).
One of the tips to improve performance was to install a thinner head gasket for higher compression. They used a cut-up aluminum can for material. How nice! No going to the Harley shop and waiting for the parts man to come back from his extended lunch down at the biker bar. Dig through your trash for parts!  Pop in a can of pop...instant power! 
Now, today, with the crappy gas we have to deal with, high compression may not be the hot set-up, so I have a hint of my own to lower compression back down to a reasonable level. Trust me. I have been a mechanic since 1973. Worked on everything from mini bikes to earthmoving equipment, so I KNOW what I am talking about.
First, make sure your Baja engine is clean before disassembling. You may have to remove engine from frame. Next, remove cylinder and piston. Place the piston in a vise and protect it from vise jaw damage with clean shop rags. Do NOT overtighten vise! Get a sharp center punch and using a small hammer, put a dimple in the exact center of the piston crown. Using a 1/2 inch drill (available at most rental yards if you don't own one, drill a hole in the top of the piston using a 1/2 inch bit. Be very careful the bit does not "walk" during drilling. Drill until there is no more resistance and you see no more aluminum bits.
 Don't go too far or you may damage the piston wristpin bosses. Remove any shavings. You do not want to damage the engine innards with any aluminum shavings. Install piston/cylinder and presto! Lower compression!  You may have to adjust the powerband to account for the lower compression. (adjusting tool available at most motorcycle shops. Just ask the service manager, he may loan it to you free of charge)
This has worked with other makes, such as the Kawasaki Pighorn,  Penton Mud Bark, Suzuki Cyclops 400  and other fine competition off-road bikes. Next hop-up hint will be how to bore your cylinder. If you have any additional performance hop up questions, ask Rick "Super Hunky" Sieman or Mr. Know-It-All...what's his name? Oh, Honda Tallbutt. Hope I have helped. Now, go vintage racing!
David Fruhling
One more thing: Do you know why they named it the Baja 100? No, not because of the engine size. They were to call it the Baja 1000, but it only made it 100 miles. Thus, the Baja 100. True story! You believe me, don't you, Rick? 
Even one more thing on the Airy-Moochey BaHaHa: When those came out, I thought it had to be the best looking, most radical (sorry) dirt bike ever. Three feet of ground clearance, etc. Of course, what did I know..? I thought the American Eagle bikes were cool, too. But at the time, anything was better than my engine-less  Honda Trail 55.  

Now this one must be taken with a large grain of salt. I don't know of anyone who has drilled a hole in the top of their piston to reduce compression, and I suspect that Dave just pulled my leg with this one. Will wait patiently for his response.

yall have an article by Matt Cuddy on your web page about these bikes. Im cleaning out my fathers garage and i believe from what he tells me thats what he has. Now ive searched and searched for info on the and cant come up with a whole lot on it. I was wondering if you knew how much there worth or if you could point me in a direction of somebody that does? Here is a picture of kind what it looks like. This is in alot beter shape though.

We turned to our good friend, Matt Cuddy, for his thoughts on this question:

Your 250 is worth as much as a Harley sprint nut wants to pay for it. You've got a good model with the short-stroke motor and the scintillex magneto (big lump on right side case). Also, it looks like it doesn't have the stock Aeramacchi frame, maybe an aftermarket? The DT frames were all rigid for short track racing; yours looks to be set up for scrambles.
It's an ERS, which means it's and off-road racing bike. Must be the stock frame. Clean it up and put it on eBay, you'll get around three grand for it. The pictures you sent were of the bike, right?  Nice, wish I'd of found it.
The motor is very reliable, with a big end on the connecting rod the size of a small block Chevy running in roller bearings. I'd say it's worth at least $4,000.00 easy. Believe it or not the bikes when set up with the right carb and camshaft/exhaust put out over 35 horsepower. And yours weighs about 230 lbs. wet.

Keep it and ride it. It's pretty rare in that condition. And fast.
Matt Cuddy
Burbank, CA


I have an 84 Honda XL350.  When you kick the starter it will move maybe an inch then stops dead.  When I turn the crank on the side of the engine with a socket it feels like the top end is ok.  After I turn the crank with a socket the kick starter will kick two full kicks and then stop dead again just like before. 
I put the bike on a stand and put it in every gear and turned the crank with a socket and the rear tire spins like normal.  If I have the bike on the ground and put it in gear then push it with the clutch pulled in the rear tire will spin freely just as it should.  The manual I have says if the starter won't move check the topend, the transmission, and the clutch.  I am not an expert but it seems to me that my problem is a bad kicker gear.  What do you think is wrong with it?
The bike was like this when I aquired it.  Getting it to run again is just a fun project.

Chances are that your kickstarter pawl is cracked or completely broken. Check this out and I think you'll find answer to your problem.
They're finally here. Brad Lackey printed up a bunch of Super Hunky T-shirts and they're available now. Sizes are M - L - XL and XXL. If you don't know what those letters mean, you're too stupid to have one of these Collector's Items. White shirts only (so far) and the cost is $20, including postage in the US. Contact Rick for any questions, or to just bench race.  Email:

Other Don't Ask Columns:

July 2011

June 2011

May 2011

Sweat-shirts are available now. Sizes are XL and XXL only. If you dont know what those letters mean, you're too stupid to have one of these collector's Items. Shirts are white, with two-colors, the logo in blue and the image in black. They're heavy duty with a crew neck and the quality is high, as it should be, because Brad Lackey made them. Cost is $30, including postage in the US. Contact Rick for any questions. Newsletter
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