Z400 Hard To Start Or Wont Start When The Engine Is Cold?

[CFM-Z440]

This question has been asked many, many times so I made a pre-typed response and now Im pinning it here in the FAQ forum.



Is your Z400 getting hard to start when the engine is cold?

Is it easy to start if you pull start it with another atv?

Does it seem to start ok once the engine gets warm?

Has it done most of, or all of that, but now wont start at all, and if it does, it barely runs?

If so...



QUOTE

Check your valve clearance. My guess is that you will find 0 clearance on at least one intake valve, meaning it is cupped and the valve is junk.

This has been a common issue with the Z400 and it's clones. The stock valves are low quality, cheap to build, 2 piece tufftride coated steel valves. These valves were a poor choice by Suzuki as they do not hold up well in a dusty environment and every so often, without warning, one will break sending the valve head into the combustion chamber where it can cause some really serious damage!

Let me start by saying that I believe that the stock air box design is a bad one which definately contributes to this problem. Dust can get between the filter and the front wall of the air box rather easily. Greasing it did not help much when I tried it. I highly recomend getting some sort of clamp on style setup instead. Poor air filter maintenance will also allow dust to get by the filter!


When dust makes it past the air filter, the dust gets pinched between the valve and seat, eats the tufftride coating off and then the soft material of the valve is exposed. The valve can not survive with out that hardened coating. Once the coating is eaten away, the valve distorts when beat against the valve seat. It "cupps" which allows the valve to recede into the head and that is why your valve clearance is gone. The camshaft is now holding the valve off the seat and not letting it seal.

If you find 0 clearance, you can Not reshim and go. The valve is already ruined! If you do try to re-shim and go, this will happen again immediately and you are risking some serious engine damage!

The best fix are stainless steel, one piece valves. The only ones I know of are Ferrea or Kibble White, but I have heard recently about some kibbles that were not properly hardened. I have kibbles in my machine that have lived 2 years now with no problems, but next time around I will probably get the Ferreas because I have not heard of any issues with them.

I wouldnt do any of this without DRZE springs, and a DID timing chain. Those are the weakest points of the z400 engine and if you have it apart any way, it is a good idea to get that stuff changed now so you dont have to take it apart again to do it later.

You can get them all from Advantage Cycle (site sponcer) He sells it as a DRZe kit that comes with everything you need except the valves. The valves you will have to buy seperate from the kit, but he has them.

The DRZe kit also comes with a DRze base gasket that will raise your compression from 11.3:1 (stock) to 12.2:1 which will make a little more power. You will need to run premium fuel if you put that base gasket in though.

I have been through this my self with my 03, and I have helped many other people with this problem on this forum.

Feel free to PM me with questions on this topic. Im a Yamaha/Arctic Cat mechanic.[/b]

[Chris102371]

Hello Im new here. I am getting ready to buy my fist quad. I am thinking about getting a z400. Have they fixed this problem on the new zs or is this just on the older ones? I would imagine they would be putting better valves and timing componets in them by now. Thanks for the info

[CFM-Z440]

QUOTE (chris102371 @ Nov 9 2007, 09:41 PM)

Hello Im new here. I am getting ready to buy my fist quad. I am thinking about getting a z400. Have they fixed this problem on the new zs or is this just on the older ones? I would imagine they would be putting better valves and timing componets in them by now. Thanks for the info[/b]

No, the components have not changed so far. You can do a lot to prevent this problem by changing out the stock air filter for a clamp on design. That combined with proper, regular air filter maintenance will keep the stock valves in good shape for a long time.

There are some members that have gotten long life out of their stock valves, but there have been plenty of them that have cupped the valves also.

[ltz470 monster]

how do i no this happend to me because my quad is doing every thing that the form sayes but i just big bored my quad and the valves were fine. and i have about 3 good rides on the new motor.

[XC Z440]

QUOTE (ltz470 monster @ May 7 2009, 06:37 PM)

how do i no this happend to me because my quad is doing every thing that the form sayes but i just big bored my quad and the valves were fine. and i have about 3 good rides on the new motor.[/b]

I would suggest checking your valve clearances, i was having an issue with my intake clearances diminishing after a few hours of hard riding. I'd suggest you send your head out to Paul at Advantage Cycle and get some ferrea valves. Give him a call, he will also be able to answer your questions faster than bumming around the forum. And if you have a K+N air filter, he will tell you to get rid of it and i now agree. +1 for Paul, and for Z400central.com!

[ltz470 monster]

QUOTE (XC Z440 @ May 16 2009, 08:29 AM)

I would suggest checking your valve clearances, i was having an issue with my intake clearances diminishing after a few hours of hard riding. I'd suggest you send your head out to Paul at Advantage Cycle and get some ferrea valves. Give him a call, he will also be able to answer your questions faster than bumming around the forum. And if you have a K+N air filter, he will tell you to get rid of it and i now agree. +1 for Paul, and for Z400central.com![/b]

ok man thanks

[ltz666]

mine starts fine when it's cold,but once it gets warm or i ride it hard,the timing goes out,& if i put it be in time it goes back out of time, the timing chain is still tight ,cause i have a manual tensioner,so is it going out of time because the the valves and clearance,or do you think it's cause the cdi box has a high speed timing advance curcit?any help would be great!kevin

[suzuki]

QUOTE (CFM-Z440 @ Nov 8 2007, 05:53 PM)

This question has been asked many, many times so I made a pre-typed response and now Im pinning it here in the FAQ forum.



Is your Z400 getting hard to start when the engine is cold?

Is it easy to start if you pull start it with another atv?

Does it seem to start ok once the engine gets warm?

Has it done most of, or all of that, but now wont start at all, and if it does, it barely runs?

If so...[/b]

were can I buy the Ferreas valve for my z400

[Hymiller926]

Hello First timer here. I have read most of the threads or forums and haven't really found the answer I am looking for. So I am helping a buddy out on his 03 z400, i have checked the valve clearance and adjusted them and both are in spec and the bike still wont start. when i press on the throttle it just back fires. Any help would be great.

[chinoduca]

Originally Posted by Hymiller926

Hello First timer here. I have read most of the threads or forums and haven't really found the answer I am looking for. So I am helping a buddy out on his 03 z400, i have checked the valve clearance and adjusted them and both are in spec and the bike still wont start. when i press on the throttle it just back fires. Any help would be great.

Are you sure you installed the cams correctly? While piston is at TDC the intake cam's arrow 3 must be perpendicular with the head. At the same time the arrow 2 on the exhaust cam must also be perpendicular with the head and the arrow 2 on the ex cam must be exactly 15 pins of the cam chain away from the arrow 3 on the intake cam.

[Hymiller926]

not able to work on the bike tonight but will surely try tomorrow and will let you know. Thanks for your help.

[Hymiller926]

i checked the cams they are like you said and the chain is right anything else. took the carb back off cleaned and blow that all out out fresh gas in it and it still wont start.

[Evans04z400]

hey man i just bought a 04 z400 and it has a ticking sound from the valves and i think i need new shims to adjust it but ... it wont start by the starter anymore ... it only starts by bump / pop starting it and it dosent run right ... sometimes it bogs and it wont idel anymore either ... i think it may be taking in air but could anyone help me ????????????????????? it will be very appreciated!!!!!!!!!! PLEASE!!!!!!!!!!

[biggiej42]

Read the first post, your valves are shot. You can not re-shim.

[Evans04z400]

yeah well i think im going to get new stainless steel valves and mabye a D.I.D timing chain but should i replace the tensioner also or are the stock ones good? i hear bad about them .....