Don’t Ask: Your Dirt Bike Technical Questions Answered

Dec. 04, 2012 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
November 2012

October 2012

September 2012

Super Sir
I got started in motocross in 1969, remember the original issue of Dirt Bike magazine, and an early interview where John DeSoto said, to pass a guy who’s difficult to pass, turn inside of them, and stomp their shift lever down, into the next lower gear.  I “grew” with Dirt Bike and the GYBDT as I progressed in the sport.  I enlisted just out of HS, and raced on a first-term enlisted salary—a 1972 Yamaha RT-2 in District 38.  After time in SouthEast Asia (Vietnam and Thailand) for 1 ½ years, I was sent to motocross heaven, Ramstein AB, Germany!   I picked up a 1975 Maico 250 GP bike from Hans Maisch at the Maico factory in Ammerbuch-Pfaffingen, outside Stuttgart.  I raced the W. German Pro circuit (MotorSportRing, Offenbach) for 3 seasons, and qualified for the W. German GP twice.   Interestingly, I and the two other USAF racers (Husky and Bultaco) all raced in the Open Class, and all did well; I finished 6th overall for the season, two years running.  

Anyway, to make a long story a little bit less-long, I was an American Honda Service Manager when I got out.  I gave up racing (at 23), due to injuries from Vietnam that got much worse.  Today, after five surgeries to repair my wrists, they are now 100%!  I’m financially secure today, and I just put a 39-year-old RT-3, back on the road, licensed in California and “green stickie’d” as well.  I bought it from a dealer in Dallas, and it is an all original bike, with 1886 total miles on it.  I’ve put about $1K into it to make it the way I wanted it, just like back in the day, overweight and ill-handling as well. 
I need your assistance. I have just gotten an expansion chamber, and am ready to jet it.  If I have top-end troubles down the road, who do you recommend for custom-made piston & ring sets?  Cylinder resurrecting?  And WHERE can I get better shocks today?  My doctor has given me the “Green Light” for geezer-class motocross/desert racing, and I’m looking for a good Maico (1973 – 1975) or Husky of the same vintage.  Any suggestions?  Oh, and I agree with you on the “Last Enduro” being the best.  Of course, thumbing my nose at the EPA and Cal Air Resources Board, just does my heart good!

With the respect that an original deserves,
Mark Hamersly
Santee, CA

PS: A clone of the GYBDT was for sale out near Sycuan Casino in June.  It was gone the next day…
Mark, the RT3 was one of the most bulletproof motorcycles ever made. To do damage to the top end on that particular bike, you have to do something really dumb, like not running oil in the gas. Just ride that beast and enjoy it. The only thing you have to really watch out for is every once in a while that kickstarter will bark back and drive your knee into your lips. So watch out for that. As far as shocks for the Maico, the only real choice is Works Performance. Give Gil a call at 818-701-1010 and he'll be able to build a set of shocks that will absolutely amaze you.


Hi Rick,
Recently my son ran our Yamaha RT180 with no pre-mix oil in the pump and caused the piston to seize. Now we are in the process of rebuilding it. We are living in Africa for the time and are pretty much on our own for this rebuild so, I want to make sure I get it right the first time.

I measured the cylinder with the only micrometer I have but it is only marked at each whole millimeter. By eyeballing it I would say that the cylinder is about 64.25mm (definitely more than 64 and less than 64.5). The existing piston is just a hair smaller. What size piston should I buy (taken for granted that the cylinder is in good shape)? I have seen Wiesco pistons at 64 (std) 64.25, 64.5, 64.75 etc.

When I removed the head I noticed that there was a lot of play in the piston side-to-side. Upon inspection of the ring gap it was clear that the gap was too much. Had it not seized I probably could have just replaced the rings. I actually rode it for another 30 miles or so after the seizure before I took it apart to see why it had lost so much power.

If I go with a bigger than stock piston (64mm) would a cylinder ball-hone be sufficient to bore the cylinder? or is it only used to resurface the cylinder? I read that other types get hung up on the ports in the cylinder.

Would love to hear your advice on the matter.
BJ Schultz
Tanzania Africa

When you ran it out of oil, it not only starved the top end but everything in the whole motor, like the crank bearings, big end on the rod, wrist pin bearing, etc. Not knowing how bad the cylinder looked when you seized it, I'd say if there are no major gouges or scratches in the cylinder, and the bore mics out to within tolerances, you can get away with a medium hone job, with the stock piston and rings. But before you do that, check for excessive play on the big end of the con rod, along with up-and-down play on the crank bearings. The 180 motors are very strong, and the original design goes back to the IT175. Did you ride it for 30 miles with no oil? If you did, expect to split the cases sometime soon, as you most likely chicken fried the lower end as well. Good luck, and is it true that a Boa Constrictor can make a decent front tire in an emergency?

I've got my fingers crossed that you have some info - advice on this. Is it possible to switch out a 1988 bottom-end with a 1989 (which has a 1990 water pump)? If so, how much will it have to be modified to work? Thanks so much for your time.
Sharma D (dirt bikers mom)

The engines look identical – water pump is in the same place, power valve, etc. Exhaust port exits at the same angle. Unless they made some major internal changes from '88 to '89 I'd say it would be possible, but ask a reputable Yamaha shop before you get wrist deep into the project.


Hi Rick,
I came across your website in looking for Ossa id information and hope you can help me. I have a blue Ossa I am trying to id. I cannot find a frame number or engine number in the bike. I will send a photo if that will help.
Thank you in advance for any assistance.
Jackie Trickett

You are not even trying. Every OSSA ever made had some numbers stamped on the steering head or had a plate attached to that steering head. And every set of cases I've ever seen had numbers in there, too. Look behind the number plate at the side or front of the steering head and you’ll find the numbers.

I snagged a little honda sl70 and that is the little bike I learned to ride on and now as an adult i picked one up but it doesnt run. I am looking at " crate motors if you will on ebay and found a lifan 125 cc motor that can bolt right up that I am considering. i also found a 200 cc motor that is supposedly a fit for a sl100 bike and my big question is what would i have to do to make a motor for a sl100 fit in a sl70 frame. I know that it may take some massaging but I am lost at where to start looking. If you think i could get that 200 in there I might because they rate it at 16 hp which would really make that thing rip nice. if you could help shine some light on this i would really appreciate it and I hope to have it cleaned up and ready to rock by next years race season 

Will Fit:
HONDA CRF50 / CRF70 / XR50 / XR70 / Z50 / Z50R / CT70 Mini Trail / z50 / Minitrail Monkey / XL70 ST70 / QA50 / QR50 / CL70 / SL70 / 70 Passport
Model: 1P52FMI-K(124cm3)
Type: Single Cylinder, 4-stroke, 2 valves, OHC Racing Head, Air Cooled, 125cc
Bore x Stroke: 52.4mm x 55.5mm
Valve Sizes: 27mm intake, 23mm Exhaust
Displacement: 123.7cc
Compression Ratio: 9.47:1
Carburettor: 24mm Racing Carb.
Ignition: CDI, 12 volt, Permanent Magnetic Stator
Maximum Power: 8.5 Kw DIN @ 9,500 rpm
Rated Power: 6.5 Kw @ 7,500 rpm
Torque: at least 8.8 Nm @ 5,500 rpm
Gears: 4-Speed, Manual Clutch, 1-N-2-3-4, 1 Down 3 Up.
Gear Ratios: 1st 2.833:1, 2nd 1.706:1, 3rd 1.238:1, 4th 0.958:1
Final Drive: 14 Teeth #420 Front Sprocket Included
Lubrication: 1.1 Litres, 5W/40 4-Stroke Motorcycle Oil, Pressure and Splash
Fuel: Unleaded

I checked their site on the Internet and the motor is supposed to fit as is using the stock motor mount plates. A word of warning is in order. The SL 70 frame is stressed in the stock configuration. Can you imagine what it feels like with twice the horsepower? And going any bigger than that you would be asking for it.


hello!I just want to know where to buy a 14t front sprocket and model or item number. so i can find it easily..i want to change my crf230f easymotard because of low speed in highway..thank you

We used a Sidewinder sprocket on our 230 and liked it a lot. We even tried a 15-tooth unit and found that the modified motor would pull it. I don't know if you've got the jetting kit in your Honda, but I wouldn't go past the 14-tooth item with the stock motor. Give Vic Krause a call at Sidewinder Sprockets and he’ll have what you need on the shelf.


have a 1998 Kawasaki kx 80 and my front forks have no pressure in then at what psi shall i fill them?

Whoever told you that you should put air in your forks? If anything, you should bleed any air out of the forks after every ride.

Wondering about the disc brake conversion you did to the Honda 230F. If I understand the article correctly, a CR250 wheel bolts right in without mods? Looking at my bike, brackets for the master and resevoir would have to be made and welded to the frame? The article was pretty short on detail. Any more info available on this conversion?
David Kunkle

You were just looking at the CRF versus the TTR feature that we ran. If you take the time to go through the project bike files, you’ll see an entire article devoted to putting the CR rear wheel on the CRF. It is a very easy project and we only had to fabricate the longer brake stay arm and modify the brake pedal a little bit.  It made the brake all whole lot better and gave the added benefit of a stronger rear wheel. Definitely worth doing.


hey i have a 08 ttr 230 and was wondering if a 13T front and 48T Rear setup is good for a bike that i mainly ride long distances but need that top end power to climb some monster hills and bad terain. im a newbie so i would grealty apreciated some advise , oh and what chain is best for that setup ? thanx
Ross Smith

A whole bunch of people are finding out that gearing up the TTR230 and the CRF 230 is really the way to go. A few e-mails back from here you’ll find some advice on a man who wanted to change the gearing  on his CRF230; follow that exact advice and you can't go wrong.


I just have to get something off my chest.
I know, being a hard-core thumper fan, I have stated my preference to 4 stroke dirt bikes over 2 smokes. I have always stated that I'm not "anti-2 stroke" but I just prefer thumpers.

I reread "What Caused the Four Stroke Fiasco" and have to update my opinion(s). Rather than buy one of these 10 hour "Crystal Thumpers" that's gonna cost me thousands a year to "maintain", I'll plant my ass on a ring-ding. THERE!
(by the's all set. the 10th of Nov; I'll have 2 more thumpers I am buying. one is another TT500 #3, stock, and 1 SR500 w/a Hy-Per Kinetics 650 bore/stroke. My new hooligan "commuter" bike)
David Fruhling

More: The Kawabunga Ninja 500 is an Excellent dirt bike! Just remove the headlight and tail light and it's the perfect bike for Ghost-Riding down the steepest hills in the Mojave!

Right next to my campsite is the two sets of very busy railroad tracks. Google "Warren, west of Mojave, Ca." for directions. Just wait for a train or two and Ghost-Ride that Ninja down the hill!


I let a friend borrow my 98 honda cr250r 2-stroke he was riding it and it jus died and locked up with him the oil was low and he put 2 cycle oil in the crankcase and didnt tell me i cleaned the carb and tryed to start it it kicked a few times then acted like it was going to start the next kick it locked up i need to know how to fix this please i miss riding
victor seale

You let a real dummy ride your bike, and now you are going to have to pay the price. At the very least, you're going to have to do a top-end job. This means you have to get a manual, read it, take the motor apart, find out what parts are badly worn or damaged, go and buy them and do the entire job yourself. Failing that, drop the bike off at the shop and let them do it. The next time that dummy wants to ride your bike, go tell him to buy his own.

I have a 1979 suzuki pe 250 it is usually easy to start usually on second kick today it dont want to satrt up very easy and it backfired twice setting the air filter on fire! it still has 7:1 compression excellent spark, and is getting gas obviously, my plug is also a grayish color. any suggestions on what my issue is??? i love this bike has never given me an issue and really want to fix it. im just new to 2-stroke bikes always been four stroke
The Suzuki PE 250 has always been a fairly easy starting bike. If it becomes hard to start, the first suspect is crud in the float bowl of the carburetor. Secondly, you might check the timing. Thirdly, the reed valves might be worn out.


i have a pw 50 and my question is why do i have to haveto hold throttle wide open to start and if you quit giving it gas while riding it will die .it wont idle anymore .is it the throttle cableor do i need a new plug or what
Charles Jobe

No doubt about it, your PW 50 is suffering from starvation. The first thing to do is look for clogged jets, or debris or water in the float. Just like the guy above. Secondarily, if you have any kind of fuel filter on the line, see if that thing is flowing properly. It’s really easy to do. Just take the fuel line off the carb and see if the gas flows freely. Once the jets are clean and the gas flows properly, it should run. The last thing you might check is the fuel petcock on the gas tank.


I used to be a huge kawisaki guy I Had a 2005 250 2 stroke.
That was untill i rode my buddys honda it felt stronger much better ride and balanced. next month sold my bike got my honda i own today gets a 10/10 used to say that about my kawasaki now i give it a 6/10
Happy Rider
Bike preference varies from rider to rider. A tall rider would not like most Suzukis because they are too short. Short riders get freaked out by the new sky-high Kawasaki four-strokes. I personally don’t care for the Hondas as they are twitchy to me and nervous over rough terrain. 


Came across your web site and thought I would ask you a question. 
I have a 1968 Suzuki TC305 with 1800 miles in great original condition.  Problem is the motor ended up with water in the right crankcase so the bottom end is seized up. I came across a local ad for a 1971 Suzuki T350.  Its a barn bike not in great condition but the motor is free.
 Question:  could I use the bottom end out of the T350 for the TC305?

Nope. The motors are completely different.

SUBJECT:  1972 MAICO 400
Hi Rick
I 'm looking at  a 72 maico 400 it has a radial fin head. Is that possible? I think its a 74 or maybe  73.  About the picture of the serial # ? The serial shows numbers from a 71?

I had a Maico radial in 1972 and the chances are that the engine cases were cast in LATE 1971.

I bought a 04 yfz 450 with a resistor kit on it and i want to put lights back on it to go night riding in glamis but i am not sure if i can just unplug the resistor and if i do that what do i do with the plug that was pluged in just let it hang and hook lights up.what do i do about  new thermoswitch can i leave it in when i put lights on the bike or do i have put it back to stock can you please help
thank you for your time hope to hear from you soon
Brian J.

Your YFZ 450 is a quad, and I don't do quads. To me, they’re nothing more than a motorcycle designed by a committee who couldn’t agree on anything.  

Super Hunky
I read your article on "Project TTR 230". It sounded great to me so I went
out and got 2003 yz 125 forks complete with brakes and wheel. But the stem
bearings don't come close to fitting. How did you make this combo work can
you help me. Parts details would be nice.

Gene Garrison
Once again, you have to go to and access the project bikes. In there, you'll find a very completely detailed article on how to make the forks fit in the steering head.


Dear Ricky
Very glad that I have found your website. Very intersting thanks for sharing. I have restores an Ossa TR77 YOM1979 but have some problems at high revs. I have re-bored engine to .75 piston and rings, seals, gaskets bearings etc.. Nonethless as I said I do have a problem at high revs it just knocks. Timing and making break are adjusted fine. I have desperatly looked for the size of the main jet but could not find in the web.I am just tryingto get from experts like you the size of the main jet. My carb is the original Bing 84 which at the time being has a main jet of 145. Is this correct or not? Also for info. purposes the slow idling jet is 45.Attached please find a pisture of my Ossa Tr77. Regards from Malta, Europe    
Pierre Ciantar
This particular question was far beyond our scope, so we turned to the acknowledged OSSA expert in America, Keith Lynas. He can be reached at  His comments:

First this model was not imported to the US, so info is scarce ... there was little info about some of the machines we did receive!

I come up with 155 for the main and 45 pilot ... I am concerned that the translation may be confusing ... he may be addressing "pinging" which can be affected by poor fuel quality, lean jetting, too much ignition timing advance, and/or compression. There are a couple thickness head gaskets available, and maybe it has the wrong one? Needle may be too lean; this is the most likely a jetting issue. Try raising it a notch; ignition timing should be 2.7-3.0 mm BTDC. Use a good fuel and mix at 32:1, never add extra oil as this can cause pinging, or it may not be pinging. He may be hearing a mechanical knock ... the most likely culprit is the magneto. I have seen some that the aluminum part will work its way loose from the internal steel hub that is cast in place. This separation is almost unnoticeable to the eye but it will make a knock ... deep knock. So we need to understand the noise more to figure out how to eliminate it.

This DVD covers the glory years of Suzuki, when Joel Robert and Roger DeCoster ruled the motocross world. It covers lots of events in Europe and gives you some inside looks at how dedicated the entire team was, from the racers themselves, to the mechanics. Those early RH and TM racing bikes were worlds ahead of everyone else back then and the result was a whole slew of world championships. Excellent racing footage throughout. The DVD runs over two hours. Cost is a mere $10, which includes postage in the US.

These were the years when Heikki Mikkola was the top racer on the factory Yamaha open class machines. Yamaha fielded a huge number of motocrossers in Europe and the USA. Even though Mikkola is the star of this DVD, Danny LaPorte is covered nicely. The emphasis is on racing in Europe and there’s even a good segment on sidecar racing. The DVD is 1½ hours long and well worth having. Cost is $10, which includes postage in the US.

For ordering info, go to: and click on STORE.

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

Previous Don’t Ask Columns
November 2012

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