Valve questions?

[Groundworx]

I have a 2005 LTZ400 that I am having trouble keeping the intake valves in spec. When I bought it, they were tight and it wouldn't start. After I had them adjusted, I had the cam chain replaced. I took it to the dunes and rode it one day, then I let it sit over the winter (about 4-5 months) I got it out the other day and put fresh gas and plug in it. The intake valves are back the way they were the first time. I have heard these bikes are harder on valves, but I don't think this is normal. Anyone have any ideas of what can be causing this?

[suzukiboy]

i could use some help here too!!!ne one, i just tore mine aprt today..

[sd1]

defintely not normal.....could be a spring issue but its a pretty simple shim setup...... ive seen before where the clearance has gone out of spec after one ride quite a bit due to the parts breaking in...try shimming them to spec now again and see how long they last...

[Groundworx]

I had mine fixed. After doing some research, I found out these bikes have weak valves from the factory. Mainly the intakes. I heard using some Kibble White valves should fix this and eliminate having to adjust as much. I went ahead and put a set of intakes and exhaust on mine. My intakes were the only ones that were bad. The exhaust valves were fine, but I replaced them anyway just to prevent a future problem. While I was in there, I went ahead and threw in a fresh set of piston rings as well. The guiides and seats were fine as well. I sold the quad shortly after. He hasn't had any problems with it since.

It looks like the factory valves just wear out after a certain amount of hours. When you start having to adjust them more often, that is a sign that they will need to be replaced. I don't know if there is another brand of valves that fixes this. I read that the Kibble Whites were the best way to go so I used those. I hope this helps you guys.

[sd1]

from your first post I had the impression it didnt have many hours on the machine, but your right the valve springs can develop a sag issue due to the type of riding and ..especially if you run an aftermarket rev box without replacing the springs..that can lead to this issue or worse, like dropping a valve.....i've used kibblewhites before, it's a decent valve for the money and far stronger than stock....hope you put kibblewhite springs in also.....regardless i'm glad you got it fixed

[Groundworx]

The machine didn't appear to have many hours on it all. However, when we got into motor, there were more hours on it than it appeared. I assume it speant most of its life in the sand.

I didn't replace the springs. These vavles actually "cup" and they can't be shimmed back into spec when this happens. I tried desperately before having a valve job done. The guy I had install and seat the valves told me the springs were fine and there was no reason to replace them. He has been doing head work on cars and motorcycles since the 60s so I trust what he said. These were not a titanium valve, they were intended to be a stock replacment. I checked and changing the springs wasn't neccesary. I sold the quad anyway.

[sd1]

that doesnt surprise me about the valves, the forging process on the stock valve is a two piece as compared to the kibblewhites which are forged as one solid piece....... i've seen to many pics of the stock valves dropping and grenading the motor...sounds like you really dodged a bullet on that one....sand always is hard on engines ..... glad the new owner is happy with it, i'm sure the valve mechanic did an xlnt job.

[Groundworx]

I am going through the same thing on my 05 YFZ450. I wasn't so lucky with it. The vavle went ahead and broke. Damaged the head and killed the piston. Fortunatly nothing made it into the bottom end. A little bit of grinding on the head and a 480 kit and she will be good to go....

[suzukiboy]

thanks fellas...slowly they have been losing clearance. I could no longer shim due to already used the smallest shim possible

[Groundworx]

Sounds like you suffered the same fate as my LTZ.

[Limited Z_400]

Valve adjustment is not an option.You will have to replace your valves and touch up your valve seats..Proper air filter maintenance will help prevent this.Most engines will run 50-60 hours before valve replacement is require.I race mx with a Z with stock valves and the clearance has not changed in 100hours.One thing you should note is the screen in the intake tube is known to come apart and ingested into the engine and damage the valves and valve guides.

[suzukiboy]

what about wiseco valves?? ANyone ever used them?

[Groundworx]

I looked at the Wiesco valves when I bought the Kibble Whites. The only reason I went with Kibble White was because I read those were a good replacment. Had I not read that, I would have probably went with the Wiesco for the name. I have used Wiesco pistons and other parts and have always had good luck with them. Chances are, they are stronger than the stocks.

[Groundworx]

Originally posted by Limited Z_400
Valve adjustment is not an option.You will have to replace your valves and touch up your valve seats..Proper air filter maintenance will help prevent this.Most engines will run 50-60 hours before valve replacement is require.I race mx with a Z with stock valves and the clearance has not changed in 100hours.One thing you should note is the screen in the intake tube is known to come apart and ingested into the engine and damage the valves and valve guides.

What do you mean valve adjustment isn't an option? That is what the shim kits are for, to adjust the clearance between the valve caps and lobes on the cam.

50-60 hrs and replace valves? That would have to be some hard riding. Even my 450s get more time that that out of a set of valves. Read the owner's manual, most manufactures recommend checking the valve clearance about every 20 hrs and shimming as needed. If I were replacing valves every 50-60 hrs, I would be changing my bike or my riding style real quick.

The air filter will help prevent clearance issues, but staying off the rev limiter will help more than anything. Over revving is hard on valves. Some people put these high rev boxes on thier quads and that will really knock them out of clearance.

The valve issue is a normal thing on the Z400/KFX400. Suzuki just used a weaker valve. I have seen quite a few of these that have had this problem. I have also seen quite a few that have never had a valve issue at all. Not even clearance.

SuzukiBoy, keep us posted on your progress. I didn't have the time to do the work myself on this quad, but it is really similar to most others. Let us know how it turns out.

[wayne1ca]

I used the wiesco intake valves and a DRZE kit. I have 30-40 hours with no problems. Probably need to recheck clearance just for peace of mind.

[Limited Z_400]

Valve lash should not change in properly maintained engine.The 50-60 hour valve replacement is more towards the guys that race and are on the rev limiter all the time.Valve replacement is part of maintenance to prevent major failure in race engines.If the valve clearance is tight you can go ahead and reshim it but MOST of the time is will be a short term fix.

[suzukiboy]

i will probably go with the wiseco..i already have a wiseco high comp. piston and i never have had any issues with wiseco,if they didn't work good i beleive they would not put there name on them..as far as hrs goi have had the same stock valves since i bought my "04" in "04" and have have at least,at least 60 hrs of hard riding and racing for two years..

[corwin06]

i just got my valves and valve springs replaced and noticed that it is hella slow now top and and power wise. do i gotta break them in and it will run normal again or what?

[cataway]

i take it you did not do the work your self ??

[corwin06]

nope. dont got the time the tools or the skillz