1999 WR400F Rebuild, won't start

3 replies to this topic
  • Joe ONeil

Posted July 06, 2015 - 06:54 AM


I need some help, I am at the boudaries of my trouble shooting skills here...


I bought a bike in a box, it was taken apart by a bike shop for the owner to assess what needed to be done. When they told him it needed a top end, he just decided to buy a new one and sold this to me. Everything was there but it needed a top end rebuild, so I decided to buy a big bore kit and install it along with a Hot Cams exhaust cam. I bought a 420 big bore kit from Lukes Racing = new cylinder, pistion, rings, gaskets, etc.


This is what I've done:


General ------------------

- Everything is together and the engine is in the chassis

- All torque specifications were adhered to, according to the shop manual for the bike

- New crush gasket on the head pipe

- All boots on the carb are seated and seal nicely, no rips or tears and air filter is in great shape


Tming ---------------------

- Double and triple checked cam timing and it looks perfect, mark on the fly wheel is aligned with the case markings for TDC, cam dots are even with the head, lobes are facing outward at 3 and 9

- Checked all valve clearances and they are within specification


Carb/Fuel ----------------

- Cleaned the carb and everything looks good with it, however, I did not yet re-jet the carb

- I've tried a few different settings on the fuel mixture screw, all the way in, backed out 1 turn, backed out 1.5 turns, backed out 2 full turns, etc.

- The carb is squirting fuel as it should

- Fresh fuel


Ignition/Spark -----------

- New spark plug

- Checked spark (got it)


Compression -----------

- Did not check compression (auto decomp with the hot cams... not sure how to check it, but it feels like I have compression based on the kick starter)



Here's what happens:


- Kick it over and I get a small amount of smoke on the first kick then nothing visible after that

- It some times feels as if it might catch .. but doesn't

- After a bit of kicking ... one loud backfire

- I get frustrated and tired of kicking  and come back to it later, then tear it down look at timing, fuel, air, etc and scratch my head



Some quesitons:


- Could it be ingition timing... and if so how do I check it?

- Could it be the coil? I get spark ... same for stator I suppose (is there a way to check it as well)... I'm pretty handy with a multi meter

- Would it make sense to put the old exhaust cam back in and try it? this would eliminate one "new" thing from the equation I suppose


I would appreciate any insight or help you all can offer, my son is itching to get on the trails with me since his DRZ400 is ready to go.


Thanks in advance for any advice/assistance


Joe O

Edited by Joe ONeil, July 06, 2015 - 08:14 AM.

  • Joe ONeil

Posted July 06, 2015 - 03:54 PM


Just found this post:


http://www.thumperta...ld +wont +start


I'll try the suggestions in this thread..


... down the electrical rabbit hole!

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

Posted July 07, 2015 - 07:47 AM


Double check you valve timing with the tensioner in place. Without tension on the chain you can be one tooth off but look to be on the marks. Also, the carbs on these can be a little fussy if the jets and passageways are not clean. Don't forget about the little jets on the outside and make sure your carb slide o-ring is in good shape and the plate is going in the right direction.

  • Joe ONeil

Posted July 07, 2015 - 09:21 AM


Thanks for the tips; 


I set it all up and checked the timing with the chain tensioner on. The first time it was off a tooth when all put together so had to reset it over a tooth and torque it all down again.  Now all is good on the timing with everything torqued and tensioner installed.


I'm digging in on the electrical tonight, I'll pull the carb and check the O-ring as well




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.