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Discussion Starter #1 (Edited)
I have a 2008 LTr 450 with the following mods done to motor..Yoshimura did the headwork(porting polishing etc)Yoshimura Exaust, Power Commander, Yoshimura Cams. The machine has been great until I installed the cams. The valves seem to come out of adjustment about every few hours of riding. I am also running a fuel atv air filter. The shop that I bring it to has been in contact with Yoshimura and no one seems to able to find an answer to the problem. The heads have stock springs, but Yoshimura says that should be just fine. Has any one ran this set up.....I am at the point where I pretty much pist at the machine and everthing else that has anything to do with that machine.:swoon2: It is not fun getting your quad out of the shop and knowing it will break within a matter of hours..
 

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I cant help with your issue but it makes me wonder about mine. I have close to the same setup Yosh exhaust, Yosh stage 3 head with yosh cams has one race on it and it is now hard to start. Which makes me think valves out of adjustment but it was dead when I put it back together.
 

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Discussion Starter #3
I don't race, but the problem your having with it starting seems all too familiar. When you asjusted the valves to the Yoshimura specs did you notice alot of valve train noise as compared to stock?
 

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My stock exhaust cam comes out of adjustment all the time. I had mine at .303 mm and a few hours later I could barely fit a .047 mm feeler in there. Then I set it to .20 mm and hours later it was .330 I turned the motor over for about a min to seat the shims before considering it done too. So, I don't know if its just Yoshi cams that have the problem. My Hotcam intake is spot on every time though.
 

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Yeah there is alot of noise with this set up compared to my hotcams I was running befor getting Yosh work done.
 

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There are a couple of issues that need to be looked at.
First is the cam journal itself. You have to make sure that the cam journals are not wearing prematurely.

If this is not the issue, then you need to have the head looked at. There could be some issues with the valve job.

Mike
 

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I have heard of the same symptoms be for, not saying what it is just giving you the info that I received.

MotoGeek has run in to this situation be for with Yoshi and their stage 3 head. if I recall correctly the conclusion was valve float.

The rider happened to be very aggressive on the down shifting and would over rev the motor and float the valves.

PM him for more info.
 

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Discussion Starter #8
A little more info..

There are a couple of issues that need to be looked at.
First is the cam journal itself. You have to make sure that the cam journals are not wearing prematurely.

If this is not the issue, then you need to have the head looked at. There could be some issues with the valve job.

Mike
Thanks for the help. I have a little more information about the issue. I had my head work done first and rode the machine without issue for some time. When I had the cams installed i had issues that same day. The valves came out of adjustment within a few hours. I was not made aware of a break in procedure(just giving all the info) and was pretty hard on the machine. Machine would not stay running..

Brought to shop they found valves to be tight.. and they adjusted..
Next After a few more hours of riding..Same problem with running

Brought to shop and they found Exaust valves out of spec and needed to replace them.Got it out of shop and noticed valve train was making more noise than previously, but ran great...went out riding and machine died on trail so-When asking them about the valve train noise, i was told yoshimura said this is normal.. That fact that it never made the noise before tells me that either it wasn't asjusted to yoshimura specs or that something was wrong..
Brought to shop and found Valve keeper split, and Intake valve guide cracked off. Replaced valve guide, keepers, then went out riding..
Brought back to shop due to the fact that it starting to act up again. Was told that my valves were adjusted with Suzuki and Yosh specs(due to the fact that there were catastrophic failures when adjusted to Yosh specs).

Does this change your thoughts on anything?

Sorry for the long winded email..
 

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There are a couple of issues that need to be looked at.
First is the cam journal itself. You have to make sure that the cam journals are not wearing prematurely.

If this is not the issue, then you need to have the head looked at. There could be some issues with the valve job.

Mike
Thanks for the help. I have a little more information about the issue. I had my head work done first and rode the machine without issue for some time. When I had the cams installed i had issues that same day. The valves came out of adjustment within a few hours. I was not made aware of a break in procedure(just giving all the info) and was pretty hard on the machine. Machine would not stay running..

Brought to shop they found valves to be tight.. and they adjusted..
Next After a few more hours of riding..Same problem with running

Brought to shop and they found Exaust valves out of spec and needed to replace them.Got it out of shop and noticed valve train was making more noise than previously, but ran great...went out riding and machine died on trail so-When asking them about the valve train noise, i was told yoshimura said this is normal.. That fact that it never made the noise before tells me that either it wasn't asjusted to yoshimura specs or that something was wrong..
Brought to shop and found Valve keeper split, and Intake valve guide cracked off. Replaced valve guide, keepers, then went out riding..
Brought back to shop due to the fact that it starting to act up again. Was told that my valves were adjusted with Suzuki and Yosh specs(due to the fact that there were catastrophic failures when adjusted to Yosh specs).

Does this change your thoughts on anything?

Sorry for the long winded email..

I had somewhat of the same problem.. I kept sucking he INT valves into the head. tighten the valves up Quad wouldnt' start cold. ran great when it did start. when it was riden for a few hours had a hard time starting..
I found the INT valves out of adjustment. I called yoshi and there is no "yoshi" specs for adjusting the valves. Use the service manual... was told this by yoshi....

I adjusted the valves. quad ran great for 2 nights at the track back to same problem... INT valves to tight again,. I had enough of it i put my stock head back on... Ran just the Yoshi INT cam.. i didnt' have any problems with anything after that.. I got rid of the Yoshi stuff though

Quad made 12WHP over stock with a stock pistion/compression
Now with my stock head back on i am at the same problem after 10 rides... I know what i am doing. I am very hard on shifting and riding the limiter. I am floating the crap out of the valves.

My next engine is being sent to ATP for a build. I wont' use Yoshi again...
 

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also. If you having this much trouble after installing the cams.. just out the stock ones back in and go riding.. make sure you check the valve clearance though. sometimes it needs to be adjusted other times it may not,

being able to ride it stock is better than looking at it in the garage making engine sounds cause you can't ride it. lol
 

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At this point, all of the parts need to be inspected. If you want to send it to us, there is no charge to inspect the parts.

You should not have any extra valvetrain noise with the aftermarket work that has been done.

Mike
 

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how big were the valves in the Yoshi head, with bigger / heaver valves it takes more spring pressure to close at high RPM same with a bigger cam. the cam may have worked in the stock head because of the smaller lighter valves as the same with the Yoshi head with the smaller cam (I think you said you had the problem after installing a bigger cam in it) you may be on the edge of the capabilities of the springs on the Yoshi head and pounding the seats out of them.
 

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Valve train noise is not normal. Noise in the valve train indicates excessive clearance somewhere or there is mechanical interference. The most common mechanical interference we see is insufficient piston to valve clearance.

Valve guides do not just break. A bent valve is usually what cracks a valve guide. A valve does not bend unless the piston makes contact with the valve. The piston does not make contact with the valve unless:
1. The cam is not in time with the crankshaft.
2. The piston’s valve pockets were not machined for the cam profile or large valves.
3. There was severe valve float. Exhaust valves are the valves that usually get bent, not the intake valves when the engine is severely over-revved.

I am assuming that all of the marks on the crank and cam were in their proper location when the timing chain was installed and the cam chain tensioner is working properly. There may be a possibility that the cam sprocket hub may have not have been pressed on to the cam correctly (The marks on the cam sprocket were not in the proper orientation with the cam lobe).

Ask the guys that assembled the top end what the minimum piston to valve clearance was. Not too many technicians do this, but if this measurement operation was performed, it would have found if there was a cam timing issue.

A rapidly wearing cam journal or cam bearing will usually increase valve lash and will not cause the valve lash to decrease. Seat wear or valve face ware is the only thing that I have found that will decrease valve lash.


Here some of the reasons why the valve adjustment may keep “tightening up” rapidly.

1. Over-revving the engine may cause the valves to bounce on the seats.
2. Bad valve jobs. A. (Valve seats that are not concentric with the guide.) B. (Hand lapping will grind through the hard coating on the face of a titanium valve.) C. (Seats that were machined too narrow.)
3. Dirt getting past the air filter.
4. Valve springs that are not designed for the cam profile.
5. Improperly designed “lash take up ramp” on the cam will allow the valves to bounce on the seats.


The rev-limiter will protect the engine/valve train during a missed shift but will not protect the engine from a stupid rider. The engine will not usually float the valves with the stock cam, stock springs, and the stock rev-limiter with the throttle wide open and the transmission in neutral. Most of the valve float problems we see in our shop are associated with over-revving the engine when down shifting.

Follow the cam / valve spring kit manufacturers recommendation when using an ignition that has an adjustable rev-limiter.
 

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Discussion Starter #15
Thanks for all of the help all..special thanks to motorgeek and ATP racing engines. I will pass this info on and keep you updated as to what we find.
 
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