help with 02 426, low compression and no start.


72 replies to this topic
  • wobblyknobby

Posted October 10, 2009 - 11:07 AM

#21

You either have a slipped cam gear or an improperly seating valve (bent, insufficient clearance). The cam gear can slip 15-20 degrees and not build compression. 15-20 degrees is hard to percieve by eye.

Why don't you take some pictures of your cams and post em' up for us to examine. The angles should be similair to the way YZhaulin took his pics. YZhaulin, that was a nice thing to do BTW.

  • 84rm250

Posted October 10, 2009 - 11:24 AM

#22

All the valve are new SS and were shimed to the right specs. So it should all be good.
I will take some pics, but not sure how to post them up. And yes thank you for posting the pics of your cams. And thanks to everyone else for there help.

  • 84rm250

Posted October 10, 2009 - 07:32 PM

#23

So are there any marks at all on the cam itself and the cam gear for when they were press'd together? Havent gotten a chance to pull the cams again yet but when i do i'll try and post pics.
Was also wondering how bad it is to keep kicking it over since it hasnt really built oil pressure yet with the oil pump.

  • 84rm250

Posted October 11, 2009 - 01:51 PM

#24

Bump for having pics just not knowing how to upload them. Any help on pics would be awsome.

  • Sider_steve

Posted October 11, 2009 - 01:58 PM

#25

you have to make a photobucket account then it will allow you to put pics up.
Here is a link to the how to do it page.
http://www.thumperta...ad.php?t=454005

  • 84rm250

Posted October 11, 2009 - 02:40 PM

#26

Sorry if they dont work, but here are the pics of my cams. let me know what you guys think.
Thanks for the help


Posted Image

Posted Image

Posted Image

  • Sider_steve

Posted October 11, 2009 - 03:56 PM

#27

Nice pics.
But I'm not sure they will help much.
It would be hard to tell from pictures if they got spun a few degrees.
They look alot like the other pictures.

  • 84rm250

Posted October 11, 2009 - 05:56 PM

#28

yeah kinda what i was thinking.

  • wobblyknobby

Posted October 12, 2009 - 12:08 AM

#29

They look close enough to at least start up. It is possible to have a little debris between the valves and seat also. Make sure the spark plug is good and make sure it is snug (not super tight tho). Did you try starting it with a few twists of the throttle, choke on, hot start on? How long did the carb sit? How much gas do you have? Is the muffler clear with no butt plug? Is the cam chain tensioner in right and set right?

Does it have any compression at all or does it spin freely? A new valve can get bent if it was spun over out of time.

How does it turn over when you carefully hold the cam chain tought and spin the engine with a wrench, with no cams? There should be resistance from compression and vacuum.

Do not worry, we will get it going. :bonk:

  • 84rm250

Posted October 12, 2009 - 11:36 AM

#30

It dont just spin over freely, i can kick it about 10 times without decomp lever before i need to rest for a min.
New spark plug.
I try'd it with a few twist, with and without chock. And hot start a few times.
Every time I time it, i have made sure it was at tdc with a lengh of wire in the spark plug hole. And using all the right marks. And then turn it over slowly about times times and check again.
Carb has been siting for about 3-6 months. I know the Ap is working.
I put about 1/2 tank of 91.
The muff is clear.
I install'd chain tensioner the way the manual says.
I havent try'd spinning it over with no cams, beside with the spark plug out. shoud i try it with the plug in? Or would that be bad for the unseated rings?

Also i'm worry'd about kicking it over so much before before the oil pump has done its job. Or will kicking it over pressorize the oil system?

I hope we can, and thanks for all the help TT:worthy:

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  • Sider_steve

Posted October 12, 2009 - 11:57 AM

#31

It dont just spin over freely, i can kick it about 10 times without decomp lever before i need to rest for a min.
New spark plug.
I try'd it with a few twist, with and without chock. And hot start a few times.
Every time I time it, i have made sure it was at tdc with a lengh of wire in the spark plug hole. And using all the right marks. And then turn it over slowly about times times and check again.
Carb has been siting for about 3-6 months. I know the Ap is working.
I put about 1/2 tank of 91.

The muff is clear.
I install'd chain tensioner the way the manual says.
I havent try'd spinning it over with no cams, beside with the spark plug out. shoud i try it with the plug in? Or would that be bad for the unseated rings?

Also i'm worry'd about kicking it over so much before before the oil pump has done its job. Or will kicking it over pressorize the oil system?

I hope we can, and thanks for all the help TT:worthy:


Always use fresh fuel,I would drain the tank and clean the carb.
And pay special attention to the pilot jet.New fuels are only lasting about a month before they become bad.
As for kicking it over too much,it isn't spinning fast enough to create any real heat inside the motor.And the oil will be getting moved in the system by kicking.

  • 84rm250

Posted October 12, 2009 - 12:23 PM

#32

its a half tank of fresh 91. I will clean the carb and see what happens. Shouldnt it at least try to start from the AP?

  • wobblyknobby

Posted October 12, 2009 - 12:36 PM

#33

It sounds like you are doing all the right things. :bonk:

You do not need to worry about kicking it alot, as long as there is oil on the cams.

Did you used to ride this bike before it blew up or did you buy it broken?

Also my 426 was a little hard to get started after a rebuild, but after a few minutes of riding it was perfect. I am sure you know but do not bring any starting fluid anywhere near your bike.

So how is the spark?

Are you wearing thick soled boots so you can get a good kick without tearing your foot off?

Do you have a flywheel puller so you can inspect the keyway as GreyRacer suggested?

I have no doubt you will get this going again.

  • Sider_steve

Posted October 12, 2009 - 12:37 PM

#34

Half a tank of 91 with half a tank of stuff that barely burns when lit with a match, it might not want to fire at all.Or is it all fresh fuel? And have you verified that the AP is actually squirting into the carb?
If it is all fresh fuel it will have a better chance of working.

  • grayracer513

Posted October 12, 2009 - 12:55 PM

#35

The accelerator pump shot may produce one ignition event, but unless the next successive intake stroke draws fuel from the carb, it won't fire twice.

  • 84rm250

Posted October 12, 2009 - 12:59 PM

#36

it only has half a tank of brand new fresh 91 octane gas. Wasnt mix'd with old stuff. carb way drain'd when it sat for so long also.
Spark seem'd good.
And i use a wire when timing and the piston is at tdc with timing marks lined up. so i think the key way is good.
Cleaning the carb and putting the cams back in later today after work to see what happens.
I got the bike after it blew up, and end'd up redoing the whole motor.

  • Sider_steve

Posted October 12, 2009 - 01:47 PM

#37

They are tricky beasts to start in the first place.The FAQ of this forum has a couple videos on starting. Need at least a little compression to help find the right starting point though. A squirt of oil in the cylinder might help the rings seal up a bit.Another thread says "the 426 is just like a woman,you have to stroke her just right to get her fired up"!

  • 84rm250

Posted October 12, 2009 - 02:34 PM

#38

yeah i was planing on tryin some oil in there next time. I'v have watch'd that vid like 5 times hopin it would help. Must just be me but i have no troubles just my woman fired up!!

  • yzhaulin

Posted October 12, 2009 - 08:30 PM

#39

84rm250. no proble posting the pics, just glad to try and help someone out. your cams look real close to mine. Even a few degrees off shouldnt cause a problem. the hot cams (intake) are adjustable so a few degrees shouldn't really hurt.
You say you can kick it through without the compression release? I couldnt kick mine through even before a new top end.
It might not be a bad idea to do a leak down check if you can find an adaptor for the tiny plug threads. a leakdown might be high without the rings seated but it might give you an idea if the valves are leaking. there should be very minimal to no leakage from the valves, especially if a valve job was just performed.
I know these 426's can be a real pain in the but to start. If my bike has sits for less than a week it usually only needs one twist of the throttle. 2 weeks or more it takes two. But I do have the A/P mod that reduces the amount of pump shot.Sometime it will backfire out the pipe, then I have to decide is it too much or not enough gas, usually a quick half twist does it at that point. Before the A/P mod it was totally different and would flood very easy. It seems every change to the carb adjustemenbt or jets requires a little different technique.
Good luck and keep at it.

  • wobblyknobby

Posted October 16, 2009 - 08:49 PM

#40

So what did you find? Did the bike start? :bonk:





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