YZ400 powered R's... Why are the YZ400's so hard to start?

[Moddedx]

Exactly what the topic says...

I witnessed a guy loose a race this weekend because of this. Why are they so hard to start?

I was thinking of goign this route, but now just may go with a 350X or 400ex enigne.

[RideRed04]

They have 12.5:1 compression stock, pain in the *** to kick over. If ya dont belive me, find a friend with a high compression 350x, and add 50cc's worth of resistance. If you hit the stroke wrong, you can hurt yourself.

[Moddedx]

Originally posted by RideRed04
They have 12.5:1 compression stock, pain in the *** to kick over. If ya dont belive me, find a friend with a high compression 350x, and add 50cc's worth of resistance. If you hit the stroke wrong, you can hurt yourself.

No offense but it is not the compression... I watch a guy with a bike kick his about 20 times in a row and couldn't get hi fired either. It was pretty cold here yesterday, but not that cold... I saw on the Yamaha page that there is a long procedure you should go through to start it.

So the compression doesn't seem to be the problem....

[DaveEX II]

The YZ400 has a hard time with getting the right combustion temp inside the cylinder. If it is cool out when you try to start it and the ignition system is even just a little off (like a dirty plug or something) the mixture in the jug will not lite. Yamaha theorizes in there attempt to creat a light engine that they did not accout for the thermal conduction in a jug with realitively little material surrounding it. They are usually fine as long as the plugs and wires are changed or maintained, but that is a pain cause the tank has to come off!

[RideRed04]

Oh, I thought you ment litteraly hard to kick over. I am guessing they are jetted a hair lean (most race bikes are) and that makes them harder to start (just like the 400ex) in addition to the thin cylender wall.

[Tommy 17]

if u guys are talking about the yz426 and yz250f the problem is that theres no compression release built into the engine its manual. if u buy the new cf450f or ktm 520s they have it and its like kicking a 2stroke or anything else. to start a new 426 or 250f u have to pull in the compression release switch kick it down bring back up the kicker leave go of the switch and kick it hard. if it does start by the 3rd time theres a little red switch on the side of ur carb that looks like ur choke u pull it out this is called the hot start it does sumtin i dunno what but it rarly works for us. the bikes are a pain in the *** to start and also another problem wit a compression release on ur handle bar is that if u lay it over and u some how hit that switch in and the engines running and more then on idle kiss ur engine good by it will blow it apart faster then u can believe. i am not sure but if i remember right the old warriors had a manual compression release on the front of the engine for the pull start. if u don't push this button in and try to kick it u can't buge that starter i don't care who u are.

[Moddedx]

Originally posted by 400ex21
if u guys are talking about the yz426 and yz250f the problem is that theres no compression release built into the engine its manual. if u buy the new cf450f or ktm 520s they have it and its like kicking a 2stroke or anything else. to start a new 426 or 250f u have to pull in the compression release switch kick it down bring back up the kicker leave go of the switch and kick it hard. if it does start by the 3rd time theres a little red switch on the side of ur carb that looks like ur choke u pull it out this is called the hot start it does sumtin i dunno what but it rarly works for us. the bikes are a pain in the *** to start and also another problem wit a compression release on ur handle bar is that if u lay it over and u some how hit that switch in and the engines running and more then on idle kiss ur engine good by it will blow it apart faster then u can believe. i am not sure but if i remember right the old warriors had a manual compression release on the front of the engine for the pull start. if u don't push this button in and try to kick it u can't buge that starter i don't care who u are.

Sounds like if I decide to go 4 stroke for my R, I may just go with a 350X or a 400EX engine.

[004exkid]

I think these bikes get alot of bad rap from former 2 stroke owners trying to start them like a 2 stroke. Yes if you dont know what your are doing,do not have it correctly jetted, or have have staled(sp ?) while on the gas it will be hard to start. Although most experinced owners with proper jetting seem to hanve no trouble. I think you just need to know your machine.

[kabd69667]

Your not going to be seeing any yz426s or crf450s at the nationals this year. They made a rule that you can't use dirtbike motors untill 2003

[RideRed04]

So will gust be ok now that the z400 is a reality? i guess none of us can use our 400ex's. The 250r's engine was once in a dirtbike (kinda):D

[Tommy 17]

whats farr goin to do i think theres gonna be alot of pissed off riders about this.

[kabd69667]

I just heard about it at the local track you can't ride a yz426f or yz400 or crf450 in any quad. I don't know what riders are going to think of this. I think thats stupid

the 250r motor was never in a dirtbike and is different than the cr motor...250r's have counterbalancers and i am sure thet the stroke is different and also gearing is different....as for dirtbike motors in quads...good ridance..i think it's cheating

[RideRed04]

Originally posted by RideRed04
So will gust be ok now that the z400 is a reality? i guess none of us can use our 400ex's. The 250r's engine was once in a dirtbike (kinda):D

That is what the kinda is for. The original atc250r engine was based on the cr (loosely, ever wonder why the technology of your '89r engine is on par with a early 80's cr250?) When the atc became a trx, they pulled a xr400 to trx400ex on us. The compression was lowered, and engine was "tuned" for torque

[DaveEX II]

Dirt bike motors in quads is cheating? Didn't anyone ever tell you that nothing comes from the factory the way it should be. Silly engineers like myself are designing these things based on there own knowledge, opinions, and the bounderies of the mighty green dollar. In my opinion more power is better. 455 in fiero, try it I know you will like it :-).