Big Decision..need Advise

12 replies to this topic
  • MichiganMXer

Posted January 25, 2005 - 06:28 AM


I've seen a couple of threads where guys are spending 5 mins to check their valves. I havent opened the motor on my 01 426 since I bought it new. It starts on 2 kicks and no smoke, bike just runs great. I need some help.

I cant really tell if the bike has slowed over the past year or two or if I'm just needing more at the track. I'm debating spending $500 to have the motor freshened w/ rings and polishing. I read the thread where guys read an article by Gorr(?) and they all cracked open their bikes only to find everything was fine. I'm not much of a gearhead and cant screw up a great running bike.

I'm thinking a pipe might help too. But again theres $500 bucks that could go to a fresh motor.

I cant have my bike blow up this summer cause I missed something. :cry:

How can I confirm whether I need a top end or if I've lost power; rather than
spending $500 bucks only to find out the bike ran just as good.

As always, thanks for the advise.

You thumpers rule.

  • Ga426owner

Posted January 25, 2005 - 06:35 AM


I would do a top end if it has never been done period.....on a 01

  • Chills

Posted January 25, 2005 - 09:59 AM


Theres a couple of things you can do....

1- Leak Down Test
2- Valvle Clearance Check

I'm kinda in the same boat you are, I have an '01 426, and its all original. I recently put a 450 cam in it, and started a race series on it last week. I'm hoping that nothing goes wrong with the top end during the season, but dont want to tear it down only to find out I wasted my $$$ and could have spent it on something else....

Although, I have to admit, the 450 Cam smoothed things out on it sooo much, it feels like a different bike.

  • SureBlue

Posted January 25, 2005 - 10:17 AM


Can you tell anything about hours and how it has been ridden? How often have you changed oil and filters?
Without knowing that, I would first check the valve clearances, and if they are fine, anyway change the cam chain, tensioner and piston. Remember if you blow it up, it is easily 2 grand to fix it. And it usually blows up without a warning.

  • MichiganMXer

Posted January 25, 2005 - 10:34 AM


Sure, thanks for the response.

I've been good about changing oil.

Almost strictly track rider, C/B, I change the oil every 2-3 rides, each visit is about 3-4 20 min moto's. So about 3 hrs on each oil change. I change the oil filter less frequently, normally put 2-3 changes per filter. I keep my air filter clean.

I've never checked the valve clearances, any pics that could help me along.

Check out the track I ride. Baja Acres.

  • Chills

Posted January 25, 2005 - 11:02 AM


Hey Michigan,

Heres a link to the manual online that one of the guys put in PDF format.


MotoMan, I think was his name originally made one in JPG format, it was nice to have, but the PDF is slightly more friendly. If you already have a metric offset feeler guage, then it will be very easy to check. I personally dont have the offset feeler guages, and they work just fine, but if you have the offset ones, it makes it slightly easier. If you get the PDF manual, the valve clearance adjustment starts on page 77...Hope this helps....

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Chills

Posted January 25, 2005 - 11:04 AM


BTW....Thats a great job they did with that track layout and avail pics at different spots, I wish more tracks did that....

  • cnorton

Posted January 25, 2005 - 11:07 AM


Do a compression check, if it spec's out you should be fine, checking valve clearance is easy, I had a 99 YZ 400 and did myself in an hour just removing the top cover and using a feeler guage, if you have your owners manual it should tell you how to do it if not go to your dealer and they can give you the info you need.

  • Fastest1

Posted January 25, 2005 - 11:14 AM


Motoman393's site will have all of the info including pictures that you will need. I wouldnt rebuild it unless it was loosing pressure during the leakdown or compression tests. Check the valves.

  • SureBlue

Posted January 25, 2005 - 11:19 AM


Michigan, I "rode" thru your track and liked it! Great way to show it. It looks like a fast one too, maybe a bit hard pack some places on dry season, but when a bit wet looked nice to me. I also mainly ride track except for the 2- and 3-hour enduros I do 2-3 times a year. If you've got some 150 hours on your bike, you know my opinion... check also my reply in thread: "Top End on my 426, what a waste of time!"
Looks like you know how to take care of your bike, so I can't tell you what to do . Anyway, wish you will have no unpleasant surprises. :cry:

  • grayracer513

Posted January 25, 2005 - 12:30 PM


If you have been keeping track of your valve clearances, that will tell you a lot about their condition. If it suddenly needs more frequent adjustment, or has gone down 3 or more shim sizes (.15-.20mm), the hard Ti Nitride coating on the valves is worn through, and you should plan to replace them very soon. If that is not the case, the bike is probably in good shape. But there are 3 things that you can do to extend and insure its health.

The timing chain should be replaced, and this can be done with a minimum of tear down.

Valve springs are cheap insurance against dropping a valve, but they require tearing down the head. On the other hand, that would give you an opportunity to inspect everything and drop in a set of valve seals. The downside is that you'll never be able to tell by looking whether your valves are going to last another year, or two, or 2 weeks before one of them cuts through the coating.

Then there's rings. If you pull the head, yank the cylinder and check it and the piston out. If it looks OK, and I'll bet it does, hone the cylinder and install new rings. If you do all 3 of these things, it will set you back about $100.

Or, if it runs alright, keep going 'til it needs the valve work. You would be taking a chance, to a degree, but you have been since you got it. There aren't any real guarantees when you're running around on a bike that produces nearly 150 horsepower per liter, even on a fresh rebuild.

  • rbm33

Posted January 25, 2005 - 12:46 PM


i chose to wait to do a top end and run the valves on my 450.

the results?? notice my post in parts and accessories. "03 yzf 450 parting out" over 2000.00 in parts to repair. i wish i woul dhave spent 300.00 on a top end timing chain gears and valve shims.

  • MichiganMXer

Posted January 26, 2005 - 07:50 AM


Thanks for the posts, I think I might check it first with a leak down tester first, anyone know if you can rent them?

Related Content


Michigan Motocross Tires by 288yz450

Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply

YZ450F 03 Sparks driving me crazy by SirAttard

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 5 replies

yz400f throttle bog by yz400fmaniac

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • * * * * *
  • Hot  28 replies

Thinking about Yamaha 250... by Arctic Pride

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  35 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.