Don’t Ask: Dirt Bike Technical Questions Answered

Jan. 02, 2013 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.

Have a question for Rick “Super Hunky” Sieman? E-mail questions to, Attn: Don’t Ask.

Previous Don’t Ask Columns
December 2012

November 2012

October 2012                     

Dear Rick.
Holiday greetings from a Triumph/Husky freak. Been a fan since the early seventies, have all the Dirt Bike and Motocross Action issues, some Modern Cycle, and read them often. My favorite From the Saddle is the one where you and a friend find the used Matchless desert sled after combing the cycle papers for a $500 value. 

I consider this column the start of the vintage movement, where a vintage bike with tons of history and tradition can be just as rewarding a ride as a new $8000 cookie cutter aluminum hand grenade. Speaking of vintage, since your project low bucks was a success, how about a project with a 650 Trumpet motor, in, say, a Husky ITC frame? I'm sure theres a 83/84 CR500 Husky frame with a blown motor waiting to be brought to life with a Meriden powerplant. I heard that this swap was popular in SoCal a few years ago, but being stuck in NE Ohio, it may just be a rumor. What do you think? 

Sit tight for a few months, as I’m now working on an article about the neatest Triumphs ever made. Speaking of Triumphs in Husky frames, I recall once when visiting in Germany in 1984, there was a man there with a beautiful 650 Triumph in a Husky frame, which is exactly what you were talking about. It’s too bad I didn’t have a camera with me at the time, because it was one special kind of bike.


Rick, howdy.
After reading the article on the worlds fastest CZ, You mentioned John Bassett. Years ago I picked up a southbay Centerport conversion in an aftermarket frame. with bassett stamped on the swingarm. The welds are the finest I have ever seen. I am convinced it is a true basset frame. Any more info?
John Feit
PS You published a photo of one of my bikes in ob A centerport cz. It is a 1974 worksbike with long travel suspension. It was on the back cover. Thanks for everything.

We did a search for John Bassett and simply could not find anything at all about him. There is a rumor that he is connected with Bassett racing headers, but we have been unable to verify that. If you find anything out please let us know.


I bent the needle on the 465's carb and am having a hell of a time finding a new one. Can these things be straightened out? I heard about rolling it between two plates of glass might work.
Garth Peterson
There’s no problem at all straightening a bent carb needle. The metal is fairly flexible and will not break easily. Two pieces of glass will probably work just fine, but you’d be better off rolling the needle on a flat plate of metal with another flat plate of metal on top. The main thing to consider is that the needle is tapered and you have to be very careful how you straighten it. While the main body can be very straight, the tapered section could still be crooked. Be careful in that regard.


SUBJECT: 1979 DT100
I have done my best to identify the bike that I received as a 1979 DT 100 F (This is from the info that you posted on the website).  My question is what other bikes of the era are similar (same engines) so that I could use them to cross reference parts and get a rebuild kit. I have no problems spending a little money to fix it up and my time is not too big of an issue.  So where would be a good place to look for gaskets/ a rebuild kit.  Also how does one “delete” the oil injection system to make the bike pre-mix only( this is something that I would guess is not in a manual).
To remove the oil injection from any Yamaha Enduro is quite simple. First, locate the plastic tube that sticks out from the right side case to the right side of the intake port. It is held in with a hollow "Banjo Bolt." Remove the banjo bolt, and the plastic tube, and find an appropriate screw that fits into the hole but doesn't protrude into the intake manifold. Use RTV red as a sealant to avoid air leaks.
Next, take off the oil pump cover on the right side case, and unscrew the two Phillips head screws that secure the pump. Go to your local Yamaha dealer's parts department and ask for the oil pump delete cover that covers up the hole that was once where the oil pump was. Now you can remove the pump, all the plumbing and the oil tank, and go to premix only. I suggest Yamalube R at 32.1.
Very simple, and now you won't be running at 15.1 that all Yamaha autolube pumps are set at. Gaskets are everywhere. Look.
I fondly recall your story in "Monkey Butt" about using cloths line for "tie downs" and thought, "I'll never make that mistake."

So, before driving 800 miles south to pick up my newly purchased TT and SR500 Yamadogs, I bought 4 new ratcheting tie-downs. U-Haul didn't have any open trailers available so I went w/a 5X8 enclosed.

Croak and I very carefully put the 650 SR in nose first. Tied it down all nice and snug. In went the TT, backwards, tied snug as a slug in a mug.

I hit the road for the 800 mile drive back to Oregon. At Gorman, I opened the trailer. Both bikes are in a heap. I re-did everything. It's about 0 degrees. Went about 40 miles and again they looked like they crashed into each other. I'm sure Interstate 5's table-top surface street crossings aren't helping the situation along with pot holes that eat "Smart Cars."

After the fifth time of this re-tying, and agonizing, I thought about breaking out the 500' of parachute cord I brought and doing a "Super Hunky" tie-down on the bikes. But I thought, "Hmmm...why?"

I unloaded both bikes, and very carefully "ghost-rode" both of them into the trailer so they landed there in a heap. THEN I tied them down! Problem solved!
David Fruhling

Now why didn’t I think of that stuff way back then? I could have saved myself a lot of grief. Thanks for the tip, even though it was not timely.
have a 1971 360 mx has been in garage for 25+ years.

What is that bike doing sitting in a garage? It most certainly should be out doing its share of vintage class racing. For those who don’t know much about that particular bike, here are some facts.

Yamaha RT1-MX – 1971. This is a second year example of Yamaha’s entrant into the open motocross class. The chassis was almost unchanged from the DT1 Enduro that was introduced in 1968 and limited the competitiveness of the RT1. Lights were stripped off of the MX version and the factory GYT kit (Genuine Yamaha Tuning) was standard equipment.

The most attractive thing about the RT1 was the price ($995), which was much cheaper than the European open bikes. Customers were also attracted to the simpler and cleaner design of the Yamaha, although serious racers never considered the open class Yamaha.

It would be three years later before Yamaha entered the open class with a serious and competitive bike that would be dubbed – YZ360A.


SUBJECT:  Timbersled Snowbike Dirt Bike Conversion
I was thinking can you make these to fit a sport bike its got more power and would ride more like a snow hawk

There are crossovers and then there are crossovers. This is a crossover that covers multiple seasons. We are talking about Crosstours, sport utes, dual-sport motorcycles or crossover snowmobiles. This snowbike is a two-wheeled dirt toy that morphs into a ski and track snow toy.

Timbersled Products Inc., of Kootenai, Idaho, has produced a rear suspension kit that takes the common off-road motorcycle and transforms it into a mountain-mauling, deep-powder machine with a single front ski. Big-bore four-strokes are the best choice for this conversion. I don’t see where they offer a street bike as a basis for their swaps. However, contact them and check it all out.

At first glance, I thought wow, what a waste of 3 very rare and VERY valuable 490 reed cylinders that came on the 83 GS models that fit the 81-82 MC chain primary bottom ends, but after a closer at least they were the 83-85 style cylinders used on the Spyder/SC gear driven primary bottom ends, and the frame being a 1980, means not such a waist of good valuable hard to find parts. But still, except for the wow factor, what a waist of time!!!!
If a stock early 80s 490 Maico weighs in the neighborhood of 230-250 lbs. depending on year, and one of those motors alone is close to 100 lbs (I know I have shipped a few), subtract a bit for 2 trannys, but add all the weight of the new hardware necessary to couple the motors, you will still be close to 450 lbs, and that thing is as wide as a Honda CBX, and with that 1980 frame with the thin wall tubing, its got to flex like crazy (not to mention vibrate like a jack hammer) and handle like a cement truck with flat tires.
Robert G.

I have a 1983 490 Maico and the actual weight of the bike without fuel is 224 pounds.  The bike has a huge Mikuni carburetor and a worse performance shock. Believe me, the power generated by that reed valve motor is awesome. I had a chance to race against 81 490s, and the difference in power is simply amazing.

I have a 2006 CRF250.It is very difficult to kickstart. Once it is running it runs great. I have replaced the crank,main bearings,timming chain and have done the valve lash. The exhaust lash is at the limit for shim size. I replaced these parts because of the hours on the machine but the problem continues. I would like your input before I throw any more time or money at this bike.

The answer to your problem is right in the Honda manual. It states rather clearly that after 15 hours of riding time under a pro, it’s ready for a rebuild. It also states that 30 hours is about the maximum time between rebuilds for a non-pro. What can you expect in the way of decent lifespan from a four-stroke single that turns almost 14,000 rpm? If you have 15 to 20 hours of time on that bike, even if you’re not a pro, chances are that you could no longer adjust the valves properly and you are ready for a $3100-$3300 rebuild. Those are the sad facts if you choose to ride one of these new four-stroke hand grenades that they call motorcycles.
Hi, I have CR250, ‘93 and I need to adjust exhaust valves. Can you please give me some input?

The only input you need is being put in a room with soft rubber walls. That way you won’t hurt yourself when you bang your head against the wall. You see, your Honda CR 250 is a two-stroke and doesn’t have any valves and it. So take some time off and read your manual and find out a few basic facts about your bike
I had recently done a top end rebuild on my 96 rm80, honed cylinder the nine yards , ran fine during the break in time . Went to ride it today and no compression I can literally kick it over with my hand no problem. Any help or answer would be great. Thank you.

Chances are that your head bolts came loose or you had a head or base gasket fail on you. Actually, having any of those top-end bolts a bit loose would contribute to a gasket giving you a problem. Odds are that some bolts have indeed come loose and hurt a gasket. Check it out and let me know.
Cotton 250, great bike , by the time I rod it, on it's last legs, and some one finished it off by stuffing it in a ditch & damaging the gear mech. Such a shame. Had a Villiers 32b(?)with a decompressor. Front end, great forks.
robert woodliff

Cotton was one of those many British bikes that went by the wayside because of poor marketing and distribution problems. It’s a shame, too, because the Cotton was actually a decent bike.
I noticed your article, searching cr500 radiator guards of all things and also live in southern Oregon. We professionally hillclimb and manufacture hillclimb swingarm extensions and parts. was wondering if you might be interested in trying out a set on your sweet cr500??

Really appreciate the offer for long swingarm, but we did the feature on a reader’s personal bike and we don’t know how he would feel waking up to a longer swingarm in his future. But thanks for the offer.
ive got an 86 kawasaki KX 500, It's too tall for me to get on,
it's in good cond, no decal's or cheap stickers on it just stock bike,
Like to get an older Yamaha MX 400B that sit's lower in the suspension.
Kansas Kirk

You could make that Kawasaki quite a bit lower without spending a lot of money. You could take an inch and a half out of the saddle without sacrificing a lot of comfort. Then, you could raise the forks in the triple clamps almost a half inch. To match that half-inch gain in the front, you can remove one coil of your shock spring and that would gain you even more reduction. So before you give up, why don’t you give these things a try.
hey i need a caborator for a 1980 175 ke,i am in alaska on a island,can you help??
John Potter

I take it that no one on that island knows how to spell the word carburetor. However, I would bet that someone there has a dictionary and you can look up how to actually spell that mythical word. When you do, you could then go to eBay and chances are very good that you’ll find someone who has what you need.
Can you tell me the year model of my serial number 3m1-005480 it's close to the one listed above just not the exact same so not sure if mine is diff

According to the information that I have, in the year 1979 the MX 100 F started with the serial numbers 3M1– 000101. 

Honda CRF230F and Yamaha TTR230R Comparison
Where can I get a 15 tooth front sprocket for the CRF230L ?
I have tried all over in South Africa & online searches.

I presently have a 14 tooth as purchased from original owner, & as you mention it can do with another step up.
Good article - thanks.

We had no trouble at all getting a 15-tooth countershaft sprocket for either bike from Sidewinder sprockets.  You can reach them at 630–513–1000. 


I have a question i bought a 04 yfz 450 with a resistor kit an i have a new head lights i want to put on it but i am not sure if i can just unplug the resistor and hook up the lights and after i unplug the resistor does the plug just hang there or does it have to be plug in to something if so what and with the new thermoswitch is that going to be a problem with the i have to put that back to stock
thank you for your time

We don’t do quads in this department. In my humble opinion, a Quad is nothing more than a motorcycle with too many wheels, too much weight, and the poor excuse to hang a cooler on the front.


how much would octane booster bring up say 89 octane fuel? up to 91?
There are plenty of octane booster products in your local store. The label should tell you how many octane you can improve compared to how many ounces of octane booster you put in the gas. Typically, you can expect 1 ounce of octane booster to 1 gallon of gas would bring you up one octane point.


Hi Rick -- er, Mr. Super Hunky!

Thanks for all of the great writing through the years! I saw this ad on Craigslist (Pittsburgh) today, and thought it would give you a laugh. I bet that this guy gets a *lot* of replies to his ad...
Ted Tarka
wanted- blown up 250F or 450F Bikes - $999 (PA)
Will pay cash $300- $1000 for a broken 4 stroke bike 250f or 450f

Could be ripped apart/basket case/ blown up

If you need Xmas cash call me first

I pick up ASAP with cash

Will pay reasonable amount



Please send pictures



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Sorry that I am just now getting around to replying to your e-mail.  What I am doing with the RT-3, is what I wanted to do, back in 1973.  High front fender, S&W fork springs and leak-proof fork seals, Boyesen reed valve, Bassani expansion chamber, K&N air cleaner, Red Wing ‘hammer-head’ shocks, Barnett clutch, Battery eliminator, forward rotated kick start lever, black dog-leg levers, dirt tires in place of the Dunlop Trials Universal (Yeecch!), real off-road pegs in place of the rubber POC items, and who knows what else.

Racing as a semi-pro in Germany from 1975 – 1977 was very interesting.  What we had to pay for things over there, you wouldn’t believe.  We all raced the Open class, and Mike Ponder was one of the other Americans racing the MotorSport Ring, Offenbach circuit with me.  He had just started riding in the dirt when he was sent to Germany.  After getting together with me, he first bought a well-thrashed 73 Husky 250.  He raced it for a season, and the maintenance drove him (and ME!) crazy!  He also was no great example of a ‘wrench.’  So, off we went to the only Yamaha dealer within 100 miles.  They had all of 7 bikes on display, six street bikes, and a lone, un-sold 1972 DT-2MX (this was in 1976!).  For the ‘honor’ of owning that DT-2MX, he had to pay over $2500!  He did, however, start finishing races instead of DNFing! 

My ‘support’ Maico dealer (near Nuremburg), was 200 miles, one way, from Ramstein, AB/ Kaiserslautern.  The bike I was given by Maico-Fahrzeugfabrik GmbH, down in Ammerbuch-Pfäffingen, was somebody’s primary race bike, which I inherited (photos attached were taken in 1975 and on the trailer in 1977).  I LIVED in catalogs from the Moto-X Fox (down pipe, air cleaners, etc.), FMF (Bilstein shocks), and, believe it or not, JC Whitney! 

I bought a 520 chain from JC Whitney in late 1975, for $10, and it was STILL on the bike, not stretched, when I sold it before leaving to a young Roy Mays in late 1977.  I have had recent communication with Roy, and he’s done well as a Pro here in the USA; he was a well-known pro, regionally at least.  What I am saying, for the most part, is the things we took for granted here in the US, just were not available over there!  We all were dependent on catalogs for our racing support.  Hell, I remember making a condenser mount for the Maico out of a 7Up can, using tin snips.

With all the realities of racing for us, as enlisted swine, it amazing that I qualified for the West German GP in both 1976 and 1977.

Here in the US, while I raced a 72 RT-2, I rode two Grand Prix, the Lilliputian GP, Magills Cycle Park, Sacramento, in December 1973. I remember finding a good line through the mud hole, and seeing Dick Mann blow by me like I was standing still, up on the median, out of the mud.  Somehow, that made being lapped easier to live with.  I also raced the Black Bart GP, hosted by my Club, the Yuba-Sutter M/C.  John DeSoto did a motocross class on Saturday, and I proceeded to get the water-truck stuck in the mud when I did a ‘gang dump’ of 8K gallons of water that evening.  I was a little drunk…I did OK on race day, got a 5th in the Open Intermediate class.  By July 4th, I made Expert at a race at Cal Expo during the State Fair, then left for Vietnam…
Anyway, just ordered more stuff from the website, which I will devour as soon as they get here.  Thanks for being YOU.
Mark O. Hamersly
Old Timers disease got me—I forgot the photos.  This time they ARE attached!  The first was taken at our practice track, where all three of us, and an occasional member of the Maico Team, and twice Brad Lackey rode (Brad lived then in Louvain, Belgium, about 45 minutes from Ramstein).  It was just on the outskirts of Ramstein Village, and the garage Mike and I shared was on the trail the Forestmeister used for travel in that area of the forest.  The one on the trailer was taken outside my on-base quarters at Ramstein Air Base, just before I sold it to come home. 
Sadly, I had surgery courtesy of the VA, for repairs I needed after being shot and breaking both wrists in SEA.  That was in 1978, three months after I returned to my home in San Diego.  That marked the end of my racing, and even off-road pleasure riding, until my 5th surgical repair of my wrists actually did the job.  The third, poor quality photo was of me, on my RT-2, taken in about June 1972, on base at Beale AFB (45 miles North of Sacramento, outside Marysville, and home to the SR-71A “Blackbird” and a mixed Wing of B-52G and H bombers).  It appeared on the front page of the Base Newspaper, as I started up an on-base M/C Club that hoisted its first race four months later, and a Trials soon after.  The green San Diego Yamaha jersey was the one I was wearing in the 82nd row of starters in the Elsinore GP that was filmed for On Any Sunday.  I’m right near the small building in the curve, on the outside (right) on the line.  The last photo is of my RT-3 as found at an on-line dealer (Marbles Motors) in Dallas, last June.

Wow, you had some pretty amazing experiences throughout the years and we’d like to share them with the readers. Thank you.

Get the first four years of Dirt Bike Magazine on discs. Those early copies are getting hard to find and the ones in the first year (1971) are going for big bucks. Here’s what you get:
*   Every issue from June of 1971 through all of 1974. That June ’71 issue was the very first issue. I worked on all of these magazines until that last issue in 1974. You’ll see a big difference in content in that last issue and the ones that preceded it.
*  Every issue has every page included. All the color pages are reproduced in color. You can print out every page if you want to, since the issues were produced in Picasa 3 format.
*  Or you can put it in your computer (or CD/DVD player) and simply enjoy a slideshow of each and every year. There are seven discs included in the package. Each disc contains one-half of a year (six issues) in order. This comes to about 4400 pages total. Here’s how to work the discs: Pop a disc in your computer and open it. An icon saying Pictures will appear. Left click it.
Another icon will appear naming the disc (ex: Dirt Bike 2nd Half 1974). Left click it. This will bring up a bunch of dates/icons. Left click on the first one.
This will open up Picasa 3 and the first page of the magazine. Go to the bottom of the photo with your cursor and this will reveal the tool bar for Picasa 3. It’s self explanatory. You can make the page bigger or smaller, rotate the page, edit the page in Picasa, advance to the next page, make a slideshow out of the magazine by clicking the arrow in the middle, or simply print the page out by going to the down arrow (far right), click it and follow the directions.
The seven disc set costs $70 plus $5 for priority mail.  So get your very own piece of history. Newsletter
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