Don't Ask: More Dumb Dirtbike Questions

And some reasonably intelligent ones too

Sep. 01, 2008 By Rick Sieman
SUBJECT: WIDE OPEN 1979 YZ400

hey
i just bought a '79 yz400. i test rode it and bought it and once i got it home a started it up running a 32:1 ratio, it runs strong and has tons of power but after about twenty minutes of ride time it started reving of its own accord like the throttle was stuck at wide open, i tried letting the clutch out while rolling in third gear to see if it would calm down but no dice. i cleaned and checked the carb, made sure the gas wasnt stuck and both were fine. i asked a yamaha tech and he says i must have blown a seal, i think he said it was the crank case seal. he says i should be able to fix it in an hour or so. so i was wondering if you thought this would fix the problem and if not what should i do? thanks.
No Name
Portland, OR

A bad crank seal would not cause the engine to run wide open. You have a massive air leak and I would first look at the reed block/manifold where it attaches to the engine. If it's warped badly on the mating surface, your engine would run on wildly.

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SUBJECT: STREETABLE DT250

Dearest Super Junky,
I am moving to a big city, and I will no longer be able to ride my beloved YZ250s out of my garage door. I am thinking about picking up an old 1972 DT250 and putting street tires on it, using it as an around-town scoot.
What do you think about these bikes, is there any particular year/size I should avoid or seek out?

Thanks,
Bert Carrier Jr.

We enlisted the advice of good friend, Matt Cuddy, who knows more about DTs than is healthy.

He notes that the 1971 DT1 was the last year with the piston port engine. After that, all the DTs were reed-caged. The 1972 was a great bike, but was kind of slow. It had good low end and mid-range and nothing on top.Matt says it's best to avoid any 1974 and up model.

The best bet? Matt swears by the 1973 250, the one with the green tank. It was the first one with a 21 inch front wheel and had good power all the way around. Now you know.


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SUBJECT: 1984 KDX250 IGNITION

G'day Rick,
I recently got my hands on an 84 KDX 250 at the right price, not long after the first 200Km run ignition "gremlins"
crept in. First no spark when hot, then hard to start cold and now no spark at all. I'm looking at replacing the lot, stator, flywheel, CDI and coil, any chance you could recommend a good aftermarket supplier that might be able to supply a kit.
Thanks heaps
Terry
Port Augusta, AUSTRALIA

Nope. Can't help. You're going to have to bite the bullet and pay a dealer for the parts.

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SUBJECT: METAL CORRODING IN HONDA CR125

I have a several bikes but the one I just purchased is a 1984 CR125R and it runs great and has just had a new top end rebuild. This is my very first liquid cooled bike and as I was going over the bike shortly after getting it i noticed that it was loosing water internally and mixing it with the crank case oil. I soon discovered that the right case cover had rotted through and was the cause of the leak.

After much searching i found a used side case cover that was also rotted but not leaking through. I wondered is this normal for the liquid cooled engines or is this a traight of the early liquid cooled Hondas only. I want to keep this bike and as we say around here " beat the wheels off of it".

Also does anyone still make a new replacement side cover for these bikes? Honda and several online vendors do not carry it anymore and the ones I have contacted do not have access to getting anymore.
Thanks,
MOTOCRAZY
Fayetterville, IN

What you have experienced is a water cooled bike that had water put in for coolant, rather than using the recommended coolant. The metals inside will corrode the cases and you've got a real problem. You're best bet is to call around to some bike scrapyards and get a used case.

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SUBJECT: NEW MAICOS

DEAR,RICK,
I KNOW YOUR SOMEWHAT OF A MAICO FAN AS I AM & I WAS JUST WONDERING IF YOU HAVE SEEN THE NEWER 2007 MAICO 250,320 AND 500MC AND THEIR ENDURO BIKES? I KNOW THEY USE TO MAKE 380'S ALSO BUT I HAVE'NT SEEN THEM ON AXEL KOSTLERS WEB SITE LATELY.

MY QUESTION IS ARE THEY STILL THE FAST&WICKED BIKES THEY USE TO BE? AND WILL THEY BE ABLE TO KEEP UP WITH THE NEW 450 4-STROKES? I DO KNOW ATK USE THE MAICO 620/700 CC ENGINES ON THEIR INTIMIDATORS!
Jeff Flick
Cumberland, MD

I haven't ridden any of the Maicos in the last ten years or so, and I've heard nothing good about them. And quit sending your emails in CAPS.

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SUBJECT: HOT RUNNING 1983 XL 200R

i have an old 83 honda xl200r and it seams to be running great. my concern is that the spark plug looks red on the top 1/3rd of the insulator. moto mechanic told me it may be running too rich so i changed main jet from 100 to105. the plug is still red and now the metal electod has a greenish tint. some times im lugging through the woods and then higher speeds up and down the local ski hill. any ideas what is causing the odd colors on my plug?
thanks,
bford
Rock Hill, NY

First off, by going up to a higher number on the main jet (you noted a 100 to a 105), you are actually richening up the jetting. A red plug tells me that the bike running hot.

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SUBJECT: WHICH DIRT BIKE?

i need to know what size dirt bike i need im 17 and around 200 pounds and 6 foot 1 Shaun Lees Summit, MO

You might be 17, but you write like you're 10 years old ... or worse. What kind of riding do you want to do? What's your skill level? These are all questions that determine what kind of bike you'll need.

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Hey man!
I have a KX 125 2001 model! It is all of a sudden smoking, and ive noticed oil on my rear fender, and on the front side leaking down from the engine on the muffler. This just started! The thing hasnt smoked a lick since ive had it! Ive had about two months or so. Its hasnt fouled the first spark plug, and it could sit for a week and it always cranks on the first kick! I want to diagnose this prob, before something catastrophic happens.

OK about a week ago, i drained all of the gas and engine oil, and put new Amsoil 2cycle racing oil, 50:1 ratio. The guy at the shop told me 3 ounces to a gallon with this oil! And since i used this oil its started smoking more! Just wondering if that was way too rich? Oh!, like i said the bike will crank on the first kick and will idle! But if i try to take off it will die and bogg down unless im at a higher rpm, But if i put it on choke it does fine!
My uncle things the carb needs cleaning, and the oil is too rich!
Jason
Jasper, AL

When you went to a leaner oil ratio (50 to 1), you effectively richened up the entire jetting. More oil = leaner, less oil = richer. Got it?

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SUBJECT: '88 YZ 125 GEAR PROBLEM

Hi ,
Just purchased an 88 YZ 125. Bike runs well but will pop into 1st gear on its own if I rev it up in Neutral. What might cause this?
Thanx
Reese
Tupper Lake, NY

You have a weak spring on the shift mechanism and when you cause a heavy vibration from the engine, it will drop into low. Not 2nd, because it won't fall up.

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SUBJECT: RETREIVING A DROPPED CIRCLIP

My son accidently dropped the piston wrist pin circlip into the crankcase on a 1999 Honda CR125R. Do you know any tricks to fish it out without splitting the case?? Also, does the main swingarm bolt simply slide through or does it screw in the last inch or so? Ours is very resistant to move.
Thanks!!
ET
Brewton, AL

Having done this a number of times, I can tell you what has worked for me. Normally, I would simply turn the bike upside down and shake it forcefully. The connecting rod should be taped to the TDC position while doing this. If this doesn't work, try dumping some gas in the bottom end and do the upside down trick again.
I've also had a bit of luck using a small magnet.

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SUBJECT: 1986 KX125 WITH NO GEARS

HI
I HAVE A 1986 KX125, I RODE IT ONCE AND THEN ALL OF THE SUDDEN WHEN I TRIED TO RIDE IT AGAIN IT WOULD NOT ENGAGE FIRST GEAR OR ANY OTHER GEAR, CAN SOMEONE PLEASE HELP.
DomoT64
Mountain Home, ID

You have two problems: your shifting pawl is probably shot and your command of the language is pathetic. The first can be fixed by a shop. The second requires study and work which just might elude you.

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SUBJECT: 2000 YZ125 SHIFTING PROBLEMS

hey,
i have a 00 yz125 with some problems that i was hoping you might be able to help me figure out. When my bike is off, i try to shift through my gears starting from the bottom. 1st to 2nd is fine, but 2nd to 3rd,3rd to 4th and so on, it acts wierd. when i try to shift to 3rd, i can roll my bike like its in neutral,for a couple of feet then it makes a clicking noise and then goes into gear.

it does that between every gear except from 1st to 2nd. when the bikes on, and i shift it into 3rd or 4th or 5th or 6th, and let out the clutch, it seems like its in neutral. i was wondering if it could be a clutch problem or tranny or shifter or something? also trying to figure out if i can diagnosis itwithout tearing it completely apart cuz i dont really know what to look for as far as wear goes.
thanks.
No Name
Magalia, CA

Why is it that bad writing and bad manners seem to always go hand in hand? First off, it's Mister Hey to you. Secondly, you probably have badly worn dogs on the back of the offending gears.

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SUBJECT: 1990 YZ250 FOULING PLUGS

i have a 1990 YZ 250, it has a lot of power, good compression,new spark plug (NGK B8ES),air filter, and fresh fuel (premium @32:1).when i ride it and open the throttle all the way the RPM's dont get as high as they should, also it fouls a new spark plug after about an hour of riding, ive cleaned the carb multiple times and adjusted the air screw,but it still wont idle or run like it should and it keeps fouling plugs. it tried every thing i can think of, what should i do next?
Jeremy
Tucson, AZ

Simple. You're jetted way too rich on the main jet. You can adjust the air screw all day long and all you'll do is slightly alter the lean/rich on the pilot circuit.

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SUBJECT: BROKEN SPROCKET BLUES

my dirt bike is a 80 cc with a broken front sprocket how can i fix it? and help my uncle fix it?
Lucas
CANADA

This might come as a shock to you, but you might actually take the broken sprocket off and replace it with a new one.
Of course, this is just a wild guess. I had no idea that your uncle had a broken sprocket.

***

SUBJECT: YAMAHA ID Article Title: Yamaha Vintage Dirt Bike I.D. Guide

hello people
i just got a dirtbike from someone and ive found the serial numbers, but, they are not on this chart...does anyone have any advice as to what i can do? also could it be that there is a different brand motor than the frame?
Greg
Greer, SC

Do you think its possible that it's not a Yamaha? Based on the fact that you didn't supply any numbers at all, I can only humbly suggest that you whack yourself in the head repeatedly.

***

SUBJECT: SHARING A STORY

Rick,
I thought you would like this story. I admit to loving equipment as much or more than riding it.

In late 2006 I bought the bike of my dreams. A BRAND NEW YZ250 two stroke. I wanted one and I figured it was near the end of its development cycle. In other words, as good as it was going to get. A bike I could leave stock.
Sure, I would upgrade as I went along, but only the necessities.

This lasted for about two weeks and out came the credit cards. Suffice to say I built an almost exact replica of Chad Reeds 2005 supercross weapon right down to a "appropriated" piston that was intended for Ricky Carmichaels RM 250.

I enjoyed the bike in a major way. It was fast, mean, and about 10,000 times better than what I need. To rebuild again would be close to $15,000.

Perfect..or almost.

I moved into a subdivision that is extremely friendly to off-road machines. The "Natural Park" near my house is 10 square miles. In 2008 "Natural Park" is the PC term for field....un-landscaped shithole...whatever.

All was going well. I thought I would be a good citizen and buy the most quiet silencer available. The FMF QStealth was new to the market, slightly expensive, but reported to be quiet. Off went my order.

The silencer fit perfectly. When I started the bike I was scared. The lack of noise made me think I left the plug in the end of the thing. Think stock KDX 200 quiet. I WAS THRILLED!

All went well until my 4 year old granddaughter saw the bike. This time she was not afraid of the sound. I said, "Kyleigh, would you like a ride?" She has been turning me down since before she could speak. This day she said ,
"Sure!' I went to the bike shop, bought her a helmet and gloves, and tossed her on the gas tank.

Rick, we have yet to exceed 10 mph. We ride safe, quiet and legal (?). So far we have logged 6.25 hours at less than first gear speeds.....never exceeding the sound and speed limits of a 4 year old passenger.

The only bike issue I have had was wet goggle lenses. It would be a lie to say a tear or two did not fall. I will soon be purchasing her a pw 50.

For all those that wonder, that FMF Q Stealth for the 2 stroke mx bikes is amazing. No power loss and the noise level is silly quiet.

Thank You for taking the time to read this.

Roland Cannon
Salt Lake City, UT

Good story and one that deserves to be shared with our readers.

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SUBJECT: THE GREAT DRAG RACE

I was wondering my friend has a STOCK 2003 yz 85 and he says his can beat my 1996 yz 125 which has newtop end pro circuit spark arresester which is faster and what are the top speeds of both thanks hayden Royalton, MN

This is very typical of a dumb question that has haunted editors for a long time. Do you think you could just have
a simple drag race and settle this for once and all? By the way, my money is on the 125.

 

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SUBJECT: 2005 WR450F BOILING GAS

i have a 2005wr450f. with a 3 and a half gallon acerbus gas tank. i have routed all the hoses away from the muffler and cylinder. but i continue to have problems with the gas boiling. i am thinking this can not be good. is there something i csn do to prevent this or just put my stock tank back on?????
Mark P.
Brighton, CO

Many of the new four stroke racers have a problem with the gas boiling in the carb, not the gas tank. You could also have your engine running hot, which would cause the carb to boil and the gas to bubble up in the lines.
You also could put some asbestos tape on the bottom of the Acerbis oversized tank.

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SUBJECT: FREEBIES

hi
i was wandering if you know where to get a free wire diagram for my 1978 Honda XL350,i just bought it.thanks Jay Bowmanville, CANADA

Oh yes, it comes free in the shop manual that you buy.

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SUBJECT: 495 KTM VS 490 MAICO

Hi Rick,

I was wondering what the top quarter mile known dirt bikes are? One time you said "490 Maico was 12.8 seconds at 93 miles per hour. " (what year 490?); What about the 81 KTM 495?
Thanks,
Toby

Even though we never timed the 495 KTM in a quarter mile, it was about two lengths faster than the Maico.

***

SUBJECT: XR500 ENGINE SWAP

hi could you tell me will a 80-81 pre rfvc xl or xr500 enging bolt into a xr500 1983 bike any info would be great .
Bush Bandit
AUSTRALIA

After checking some manuals, the frames look very close. You might have to weld on some different pipe brackets.

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SUBJECT: KICKSTARTING WOES

My son is having trouble starting his 250wr dirt bike it will not start on the kick start how can the fix this Jackie Conception Bay South CANADA

What kind of a WR? Husky, Yamaha? Year? Perhaps the air in Canada is too thin to let your brain transmit important information.

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SUBJECT: FINDING CHINESE PARTS

My son has a Baja 125 dirt bike he bought from a friend. His brother wrecked it and bent the front fork and rim. We are having a hard time finding replacement parts for it. Any suggestions?
Mary Kaye Irwin

Unfortunately, you have one of the Chinese knock off bikes. Fortunately, I have a contact for the importer: Good luck.

BAJA MOTORSPORTS
BAJA INC.
P.O. Box 61150
Phoenix, AZ
602-443-9180 or 888-863-2252

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SUBJECT: '79 ELSINORE FRONT WHEEL SWAP

Hi Rick,
Mark here from Winkler Manitoba Canada. I am writing this email in regards to getting the RIGHT info for my 79 Cr125R Elsinore. I have a 23 inch front rim, and it's tire is ageing and cracking, and so is the rim. I have a 21'' front rim for a 03 cr25 in my garage with a tire waiting for a good home. No one seems to think I can re-lace the new rim onto the old I admit I am not the smartest when it comes to bikes, but I am just keeping it going for my kid.

The bike has new rear shocks, new chain rollers, new chain and sprockets, new piston rings and LA sleeve, new carbon fibre reeds, rebuilt exhaust, new shoes for breaks, my old 03 cr250 bars, new terry cables all the way around, and a new factory air filter.

This thing is more fresh than my 03 250! I got it at the age of 16 and I am 36 now, this thing will be with me for life! The Achilles heel is that front rim/tire, and the carb boot is starting to show signs of age. I don't want to restore it and turn it into a museum piece, I just want it healthy and running safely for my son to play with it. Any, and all help would be very much appreciated. And thank you very much for your time and dedication to our hobby. Here's a picture of the bike.
A sincere fellow dirt biker,
Mark Czoch.
Riley Krahn.

 

It should be relatively simple. If the spoke numbers are the same, installing the 21 inch rim should be no sweat. Good luck with the project.

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SHAMELESS PLUG
Man, I've got books, posters and all kinds of CDs. This makes the ideal gift for someone who enjoys living in the past. Website:
www.superhunky.com

Here's the source:
Rick Sieman
36607 W. Costa Blanca Dr.
Maricopa, AZ
85238
Email: superhunky@gmail.com

Paypal, Check or Money Order OK - No plastic

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