450 ate alot of dust.

4 replies to this topic
  • j-dub1

Posted March 06, 2013 - 12:21 PM


A buddy of mine brought his 09 yz 450 over to my place. He said it would hardly run, and backfired alot when it did. I told him I would give it a look and just figured it had a gummed up jet because of sitting to much.

I pulled the seat to check the air filter and almost fell over, the filter had passed alot of dirt. The cage was coated with it, the intake was also coated. Digging deeper I realised the dirt had plugged the jets in the carb so bad the bike wouldnt run.

So I am just a hobby mechanic and need some advice from people that deal with this stuff for a living. So the bike has not broke yet, how risky would it be to tear it all down removing as much dirt as possible, put it back together and ride the thing? I would like to avoid a catastrophic engine failure. Would a rebuilt head, piston and ring be a better move? With that much dirt should I be concerned about a bottom end failure in the future. Advice will be appreciated.

Ough ya, 1 more thing this bike looks almost new from the outside and if I had to make a guess it has about 10 hours on it. Thank you for your time. John.

Edited by j-dub1, March 06, 2013 - 12:33 PM.

  • grayracer513

Posted March 06, 2013 - 03:23 PM


If there's no evidence of damage, clean the carb, the intake boot, and change the oil. Then run it to see if it seems OK. Teach him how to clean and oil the air filter while you're at it.

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  • YamaJet

Posted March 06, 2013 - 06:59 PM


Maybe check the valve clearances (i.e. intakes) and keep an eye on them.

  • j-dub1

Posted March 08, 2013 - 12:05 PM


Thanks for the replies guy's. Greyracer, I see alot of good sound advice given by you throughout this site . I am sure everyone appreciates it, I know I do.

So like I said, this thing ate alot of dust. After asking many questions, I found out that a fella at the track offered to quickly clean the filter on site. So to make a long story short this guy took the bike and brought it back with a cleaned filter. But now I know the guy used gas to strip the filter of any oil, then never put any filter oil on it. Nice guy, very helpful.

So I can see the valves, they look almost to clean no carbon build up. And their is a very hard ceramic build up on the valve, where the rod portion connects to the valve. Is this normal. It looks like the heat from the valve body melted the dirt to a semi-liquid. All I can describe it as a ceramic blob. Kinda curious what you think of this, and if it changes anything as far as a rebuild or not.

Sorry so vague on the description, hope it made since. John.

  • grayracer513

Posted March 08, 2013 - 12:48 PM


No oil, huh? Nice. He should have left it off and just run the screen so it would be more obvious that there wasn't a filter.

No idea what to make of the "blob". Is it exactly the same on both valves? Uniform shape all the way around the stem?

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