Don’t Ask: Dirt Bike Technical Q&A

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 dirt bike questions for Rick "Super Hunky" Sieman? Send an e-mail with your name, vehicle year, model and a detailed description of the problem to Don't Ask at editor@off-road.com. Don’t forget to be as complete as possible with the description of your bike and its problems.

Previous Don’t Ask Columns:
August 2011

July 2011

June 2011


SUBJECT: LONG ROD 125 CZ?

Dear Mr. Sieman,

I hope this email finds you in improving health. I have a "don't ask" question and was too dumb to figure out if there was a hyperlink to that forum so I am emailing the question to you instead, and will return to the forum to see if you post my question and your answer. If I am in error I hope you will thoroughly lambaste me in your reply. 

Question:  Have you heard of a "long rod" CZ-125 (1971) that has an extra fin under the head. There is one posted on eBay right now and I've never heard of this. I had a CZ-125 back in the day and it did not have a head like that (that I can remember). Any info would be greatly appreciated. 

BTW - I really like the new T-shirts will be ordering one for sure!
Thanks and take care,

Steve T.

This called for a visit to Keith Lynas at http://www.ossa.planet.com/, because he knows more about these bikes than is considered healthy. Here’s his response:

I call it BS ... the only reason you would long rod anything is to tame the power "hit" and increase torque (if the rod ratio used is correct for leverage). Somehow I don’t think "taming" is a good thing to do to a 1971 CZ125, makes no sense.  And, as Judge Judy says, if it doesn't make sense then it isn’t true!

The head does look different than the original ‘71 125, but could this be an enduro head? Or from a newer model ‘73-74-75? (I don’t know off hand.)

Also the extra fin on the head really doesn't accommodate a long rod; the cylinder would need to be taller, but an additional fin at the base of the head does not make the cylinder taller. A spacer plate at the cylinder base would make the most sense if this mod was really done, but personally I would use a short rod for building one of these. Long rod – where do people come up with this stuff?? 

The machine looks nice and kinda correct/original and you don’t see many 125 CZ's around and guys do want to race them, at least until they feel the peak power.

Take care,
Keith
www.ossaplanet.com

SUBJECT: KDX200 REPAIR QUESTION

Dear Rick:
I have a 1984 KDX200 that dies out after a few minutes. I tried cleaning gas tank, fuel lines and carburetor, same thing.
Any suggestions?

Thanks in advance,
Rich

In addition to being mechanically sound, a motorcycle two-stroke engine needs to have the following things to run properly: spark, spark at the right time, and fuel. If your bike is in time and you have a consistent spark, then you can trace your problem to a lack of fuel. Now you may have cleaned your tank, fuel lines and carburetor, but did you clean the jets out thoroughly? Throughout time, varnish can build up in the small holes of the jets, causing all sorts of grief. You should take some contact cleaner and clean each jet out thoroughly, paying particular attention to the tiny hole in the pilot jet.  Once you do this, chances are your bike will run consistently and properly.

SUBJECT:  YZ 85 TROUBLES

Hi Rick,
I have a 2000 yz 85 And when i start it up and put it into first gear I let off the clutch (slowly) but then it Jumps forward about 3 feet and dies out. what can i do to stop this?
No Name Given

I would bet you a substantial amount of money that there is some sort of crud or water in your float bowl. This way, the bike will start and idle, but when you put any sort of a load on the engine, the crud/water will get sucked up into the main jet causing the motor to stall. It will do this again and again until you take the carburetor apart and cleaned out all of the debris, paying special attention to the jets.

SUBJECT:  WHO DO YOU THINK YOU ARE?

Mr. super flunky
just who the hell do you think you are.  people write in and ask you questions and half the time you don't really answer the question and you give them a bunch of greef. i dont think that's classy and I guess I got to ask you again just as you think you are anyways, so why don't you just go %*$%(&%$%+@ yourself and your pets.

I aint your friend

Chico from LA

My dear Mr. Chico,
You represent a substantial portion of this modern generation. That is, poorly educated with marginal intelligence. Yet, you still want to shoot your mouth off at those who know a whole lot more than you do. Your writing and spelling indicate your intelligence level, which is probably about the same as a poorly trained Chihuahua. Now go away and don't e-mail again.

SUBJECT:  GOOD OLD BSA

I had a BSA 500 in the mid ‘70s. That bike took me places I should not have been and I survived.

Phil

I can share your sentiments, as I had a Triumph 650 in the early ‘60s. And like yourself, I should not have survived many of the situations that the bike took me in. Actually, I put myself in those situations and the bike was merely the vehicle. Still, I wouldn't trade those days for anything.

SUBJECT: YAMAHA VINTAGE DIRT BIKE INFO
im looking fore info on the dt 100 bike engine no starts 1N1 frame no 1N1-132575

Dave

Your DT100 is sort of unique and my ID chart tells me that it was an England only model. It's a 1976 or 1977 bike, and for all practical purposes they were identical.

SUBJECT:  YAMAHA VINTAGE DIRT BIKE GUIDE
have a yamaha 250cc #450206131 can u tell me whatb year it is

Troy

You have a 1974  DT2C.  The serial numbers on that particular bike started with 450500101. Yours falls right into that range. By the way, your spelling and grammar are pathetic.

SUBJECT:  YAMAHA VALUE?
I have a 1974 Yamaha MX125 with all original parts in excellent condition. I'd like to know what it's worth.

Jim Stockton

If the bike looks like it has been restored and is proper running condition, you're probably looking at somewhere in the $1500-$2000 price range.

SUBJECT:  DOES IT NEVER END?  YAMAHA VINTAGE DIRT BIKE GUIDE
Just picked up OLD 125 YAMAHA SERIAL # 3R9-002438 I NEED TO KNOW WHAT IT IS IF YOU COULD HELP ME OUT.

David Frederick

Your old Yamaha is an IT-125G, H, J or K model. They were made from 1980 to 1983, and for all practical purposes are the same bikes. I could look up the exact number and find out which year it is, but quite frankly, I'm getting burnt out on the Yamaha questions.

SUBJECT:  THIS IS THE LAST ONE – I SWEAR - YAMAHA VINTAGE DIRT BIKE GUIDE
i bought a yamaha, serial # DT1F-132087. i was trying to figure out what year. i cant seem to find DT1(f). can anyone help. It's a 250.

Charles

This one can be a bit confusing. Even though the ID numbers tend to indicate that the bike was a DT1. When you take a look at the actual numbers, they tell you that the bike is a 1972 DT2. According to my charts, the DT2 numbers started with DT1F 105101. That would definitely make your bike a DT2.

SUBJECT:  COUNTERSHAFT SPROCKET SEARCH
Does anyone make an offset countershaft sprocket for my '03 Yamaha WR450f? I turned down an oem rear sprocket to use a spacer back there with longer bolts, but I can only put a limited spacer on the countershaft sprocket w/o severely limiting thread contact. As it is not, I've spaced it out approx 5-8mm and used lock-tight, but impossible to use the tin nut keeper anymore. A constant worry even with the lock tight. Maybe I should just cut my losses and switch to a narrower rear tire even though I just bought this one. :(

Rene

If anyone can answer this question, it’s Sidewinder Sprockets. You can contact them at 630-513-1000.

SUBJECT: CHINESE KNOCK-OFF BIKE PARTS
we have a 90cc Panterra dirt bike & need to know what type of spark plug to get?

Thank you
Christina

The plug that you're searching for is a CR7HSA (NGK).  But as long as the bike is not running, you want to either sell it or turn it into a decorative coffee table base. I am no fan of the Chinese bikes and that Panterra ATV is no exception.

SUBJECT:  HONDA CRF230 FEEDBACK
Rick,
First off thanks for all the great articles over the years. Been reading since the old Fla. Winter Am series.Watching Gary Jones on a Honda then Can-Am Pierre Karsmaker on a Yamaha.CZ,Montessa,Bultaco the good old years. Bad Brad Lackey was my childhood hero. Anyway Im old and bought a crf230f.

Following your articles. Did the uncork works great. My question,what do you feel is the easiest and best forks to use for the DIYer. Also do you feel the gearing and tire selection the best for the FL sand Im only 130lbs. Thanks for many years Rick.
Paul
WPB FL

Good to hear from you about the old days. Regarding the best forks for the CRF 230? At first I tried a set of conventional 1986 CR 125 forks and they worked quite well. Because I was doing a project bike, I later experimented with a fairly modern set of CR 125 upside down forks. While these worked a little bit better, they were not that much better than the conventional ‘86 forks. It requires welding a spacer on the steering head to get the ‘86 triple clamps to work, but it's not that difficult. By the way, I still have those ‘86 forks somewhere in my garage and you can reach me at superhunky@gmail.com if you're interested.

SHAMELESS PLUG - VINTAGE POSTER SET
Here’s something to put over those bullet holes in your living room or garage. Four great posters of legendary MX bikes. These posters are 2 x 3 feet in full color and printed on heavy coated stock. They feature:  Bob Hannah’s lightning bolt OW40 Yamaha, Joel Robert’s famed RH 72 Suzuki, the red rocket Hondas of Brad Lackey and Jim Pomeroy and the Three Decades of Suzuki poster. You can have all four for $20 plus $7 for mailing in a sturdy protective tube. Paypal address:  superhunky@gmail.com   Website:  www.superhunky.com

Have a dirt bike questions for Rick "Super Hunky" Sieman? Send an e-mail with your name, vehicle year, model and a detailed description of the problem to Don't Ask at editor@off-road.com. Don’t forget to be as complete as possible with the description of your bike and its problems.

Previous Don’t Ask Columns:
August 2011

July 2011

June 2011