YZ400 Won't kickstart after Hotcam install


17 replies to this topic
  • bigmatthew46

Posted December 11, 2007 - 06:53 PM

#1

I recently put a Hotcam in my 99 YZ400. I followed the directions and I thought I had them correctly aligned. Now I'm not so sure. I just changed the exhaust cam and the valves were in spec. I made the mistake of putting an accelerator pump cove on the bike at the same time. So I don't know if it's cam or carb related. I removed the carb and cleaned everything I could. I put a plug in place of the stock decompression release and now I can't kickstart the bike. I got to start by pushing it and I rode the 1/2 hour to break the cam in. After that I can't kickstart it again but it will push start. When I kick it it doesn't really do anything but it will pop after several kicks. Any ideas? I'm coming off a KDX200, RM250, and a Banshee so I'm new to the 4-stroke game. Thanks.

  • 642MX

Posted December 11, 2007 - 07:23 PM

#2

How did it run after you push started it?

  • todds924

Posted December 11, 2007 - 08:58 PM

#3

I recently put a Hotcam in my 99 YZ400. I followed the directions and I thought I had them correctly aligned. Now I'm not so sure. I just changed the exhaust cam and the valves were in spec. I made the mistake of putting an accelerator pump cove on the bike at the same time. So I don't know if it's cam or carb related. I removed the carb and cleaned everything I could. I put a plug in place of the stock decompression release and now I can't kickstart the bike. I got to start by pushing it and I rode the 1/2 hour to break the cam in. After that I can't kickstart it again but it will push start. When I kick it it doesn't really do anything but it will pop after several kicks. Any ideas? I'm coming off a KDX200, RM250, and a Banshee so I'm new to the 4-stroke game. Thanks.


Double check your intake valve clearance...sounds like they might be a little tight. Does the bike idle fine when it is running?

  • Birdy426

Posted December 11, 2007 - 09:13 PM

#4

Check your exhaust valve clearance as well...the hot cams instructions don't say anything about the autodecompressor pin holding the valve down...you have to release the flyweight mechanism to retract the pin in order to get a good measurement on the exhaust valve clearance.

  • grayracer513

Posted December 11, 2007 - 10:03 PM

#5

...you have to release the flyweight mechanism to retract the pin in order to get a good measurement on the exhaust valve clearance.

Not if you check the clearance at TDC as instructed. The decomp pin rolls out of contact at about 50-60 degrees BTDC, and is not a factor in valve clearance.

  • bigmatthew46

Posted December 12, 2007 - 05:53 AM

#6

I followed the instructions the best I could. The bike ran fine after I push started it. It ran good before I messed with it also.

  • grayracer513

Posted December 12, 2007 - 06:46 AM

#7

Does the bike feel like it has very low compression when kicking? Or does it feel about like a healthy 300cc two-stroke?

  • jayh300

Posted December 12, 2007 - 08:33 AM

#8

let me try to remember all the mistakes when i did mine..... when you said the valves were in spec, was that before the cam change ? I don't have that paperwork in front of me, but I am pretty sure the valve spec is different from the stock cam to the hot cam. Ever one i read about in the "search" mode talked about a shim change and I know mine needed a shim change to get it in spec. I also got mine 1 tooth off in the initial install. It does not take very long to re-check the timing and valve clearance.
Also, since the cam change, my cold starting ritual changed. My 400 was a no throttle hand on the master cyl. Now it likes a couple of blips of the throttle and really starts better cold with the throttle open just off idle. You still roll it around till it gets on tdc, then let the kickstarter back up to the top like you used to and give it a full kick. Once warmed up it does not matter where it is when you kick it. I don't have a good answer as to why my starting ritual changed, but it did.
Don't get to frustrated with the cam. I was almost to the point of putting my manual one back in.. once you figure it out you will love it. The initial "hit" on mine is gone and the power is way more usable. And it will bump start now with no problems.
jay

  • Yz400Flyer

Posted December 12, 2007 - 09:01 AM

#9

Like Gray and jhendr3702 have posted, check the timing.

I had mine one tooth off (had 13 pins instead of 14). The bike just popped after a ton of kicks and I finally got it running. After running it for a while (it seemed fine to me) it would only start with the choke, which was wierd for this bike. So I checked my stuff again and found the error, after that it started on the second kick.

I'm not sure about the stuck kick lever tho....

Hope you get it fixed without too much headache! :banghead:

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • grayracer513

Posted December 12, 2007 - 11:04 AM

#10

Like Gray and jhendr3702 have posted, check the timing.

I had mine one tooth off (had 13 pins instead of 14).
The bike just popped after a ton of kicks and I finally got it running. After running it for a while (it seemed fine to me) it would only start with the choke, which was wierd for this bike. So I checked my stuff again and found the error, after that it started on the second kick.

I'm not sure about the stuck kick lever tho....

Hope you get it fixed without too much headache! :banghead:

Those using a Hot Cams or other aftermarket product made for a 400/426 need to ignore the count of pins between the cams and time the cams as you would on a stock 426. The altered inter-cam pin count is ONLY for using a cam originally made for a 450 in a 400/426, and does not apply to any cam made for the earlier engines to start with.

  • jayh300

Posted December 12, 2007 - 11:12 AM

#11

Those using a Hot Cams or other aftermarket product made for a 400/426 need to ignore the count of pins between the cams and time the cams as you would on a stock 426. The altered inter-cam pin count is ONLY for using a cam originally made for a 450 in a 400/426, and does not apply to any cam made for the earlier engines to start with.


Correct... as usual. The hot cam timing is the same as the stocker. I guess I failed to get the slack in the chain on the correct side and got mine off in the initial install....
I have also learned at this point in my wrenching career, I only do 1 mod or change at a time. It is easier for me to find my mistakes.
jay
:banghead:

  • Yz400Flyer

Posted December 12, 2007 - 07:58 PM

#12

Correct... as usual. The hot cam timing is the same as the stocker. I guess I failed to get the slack in the chain on the correct side and got mine off in the initial install....
I have also learned at this point in my wrenching career, I only do 1 mod or change at a time. It is easier for me to find my mistakes.
jay
:banghead:


Sorry for the misleading information. I forgot about the hot cam set up :busted:

  • bigmatthew46

Posted December 14, 2007 - 06:13 PM

#13

I checked my valves tonight and both exhaust valves are at .35mm. Would this cause not enough compression to kickstart the bike. It seemed to run ok after I kickstarted it.

  • grayracer513

Posted December 14, 2007 - 10:12 PM

#14

I thought you said the valves were in spec when you finished? Now after you've run it a couple of times, both exhausts (which I would have expected you to have had to reshim after the Hot Cam went in) are .10mm loose. Hot Cams calls for .20-.25mm, stock is .25-.30. Loose valves do not reduce compression, but retarded cam timing with an auto decomp cam will. Shim the valves to the right clearance, and check the timing again.

  • bigmatthew46

Posted December 15, 2007 - 06:30 PM

#15

I adjusted the cam timing today and it still won't kickstart. Now I can't even push start it. I turned the motor over until I could see the "H" shape in the sight in the fly wheel cover. There happens to be 2 but I used the one closest to where my cams were lined already. The bike seemed to have more compression but it still wouldn't start. I'll try again tomorrow. I guess my timing is still off?

  • jbrooks26

Posted December 15, 2007 - 07:25 PM

#16

OK, first you need to align the I with the two notches in the sight hole. It will be right next to the H, but it is important that the I is lined up. It is not good enough for it to simply be in the window. There is only one H on the flywheel, but the crank will spin over twice for every single revolution of the cam sprocket. At this point it may be easiest to start from scratch and retime the cams. If I were doing it I would place a plastic straw in the spark plug hole with the plug removed to verify TDC. Then I would veify that this coincides with the I in the window. Next you will install the exhaust cam lining up the timing marks with the top of the head and the lobes facing toward the front tire. Route the timing chain tight on the exhaust side keeping the engine at TDC and the timing mark on the cam aligned with the top of the head. I would tie this with wire or a zip tie so that it does not move. Next install the intake cam so that the timing mark is lined up with the top of the head while the chain is tight across the top. This is all in your manual, but as I recall this is how I did mine. I too had trouble with the Hotcam install but the problems I had were all self induced. You may want to do a leak down test while you have the cam chain off, just to rule out bent valves or leaky rings and such. I have some pictures of a home made leak down tester if you need them. Hope this helps,

Josh

  • grayracer513

Posted December 15, 2007 - 07:32 PM

#17

Maybe. There are 3 "vertical" (radial, actually) lines on your flywheel. Together they form an 'H' and an 'I'. TDC is the 'I', not the 'H', and it is the farthest mark clockwise, or to the right, of the three. This means that it is also the last one to appear in the window. At this point, it may be time to verify the flywheel is correctly indexed. Pull the plug, insert a Phillips screwdriver long enough to touch the piston at TDC, and then verify that the TDC mark occurs as the piston just reaches its highest point. If it doesn't, the flywheel key may be sheared or missing.

  • camman

Posted December 16, 2007 - 09:44 AM

#18

Go to the Hot Cams website they have a cam installation and shiming video for the YZ250F. This should be close enough for your YZ400F.





Related Content

Forums
Photo
Supercross

Wilson the Blue Privateer by jetfuel


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
Forums
Photo

Snake pit oct 30th by The Anvil


Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies
Forums
Photo

The "going back to the other darkside" adventure... by Monk


Dirt Bike   Make / Model Specific   KTM   250/350/450/505 SX-F & XC-F (4-Strokes)
  • Hot  113 replies
Wiki
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info


Articles
  • 0 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.