YZ426F cold start problem / question

camrider · Feb 14, 2004

I purchased an '01 426 today. Seems to be in good mechanical and cosmetic condition. It was a bit cold natured and didn't like to idle until it warmed up, but once it reached operating temp, it ran fine.

Got it home and it started right up on the second kick. It sat for about 3 hrs. in the shop and I tried to start it up again. I wore my a$$ out trying to start the bike! It never happened. It did however pop a huge "BANG" of a backfire one time. I think that I have the "starting" sequence down, but I still couldn't get it to start. Maybe I accidently touched the throttle before trying to crank it? I tried with the choke out a few times, then I tried it with the "hot" button out. I continued to try to start it for about 15 minutes with no luck. When my legs turned to rubber, I had to give up. :ugg:

Any suggestions?

By the way, I am by no means stating that the bike is a lemon. As I said above, it ran fine when it warmed up. I'm just a newbie to the NEW Hi-per 4-strokers and could use a little help/info.

Hick · Feb 14, 2004

They can be tempermental.

If you flood the bike you can foul the plug, so you may consider checking that, although the backfire would suggest it is still working.

If you suspect you are flooding the bike, pull the hot start out, then kick it over w/ the decomp. pulled half a dozen times.

Then start over.

You may try priming the motor by twisting the throttle, the carb has an accelerator pump that squirts gas into the carb throat when you operate the throttle. Find TDC, twist once, then kick it. In my experience this worked better than using the choke and, counterintuitive as it may seem, was less likely to foul a plug than trying to use the choke.

Also, I always thought the reason they made the idle speed knob so large and accesible is they knew you would be using it regularly. My "drill" with my YZFs was always to turn up the idle about a half turn each time I started it cold, so it would idle unattended w/ no choke, and I would let it run while I put on my backpack, protector, helmet, goggles, gloves etc.

For whatever reason, I found that one sure-fire way to make these bikes impossible to start is to warm it up partially and then kill the motor. :think:

jmics19067 · Feb 15, 2004

If you think you have the "drill" down, with the choke on while cold, choke off when warm, and hot start when flooded, finding top dead center, pull compresion release, push kick start just past top dead center, release compresion release, let kickstarter come all the way up and give a healthy boot.

Try resting your one hand on the front brake master cylinder, took me a long time to realize that as I was kicking I was twisting the throttle a bit without knowing it.

mxmatt426 · Feb 15, 2004

If you touch the throttle when starting....change the plug. If you run the bike without proper warm up.... change the plug. When you change the plug buy a CR8EK your leg will thank you. Before you shut a 426 off give it a couple of hard revs. It will help for restarting. If the carb is jetted correctly then you will never need to use the hot start. You can fit your 426 with a YZ450 exhaust cam, to eliminate the compression release, and it will kick like a 2 stroke. I have not changed mine over to the 450 cam because once you get used to the drill, it comes natural.
Once the header starts to glow red you know the engine is warm and ready for use. Never start the engine and shut it off without warming the motor and reving it up (way up). Turn your idle way up, the bike should be on a fast idle when the choke is on. I leave my choke on for a few mins. in the winter and probably 2 mins. in the summer. Once the engine is warm it should idle about 2000 to 2500 RPMs. Good luck!

camrider · Feb 15, 2004

And I thought I was getting away from some of the tempermental 2-strokes issues! :eek:

I don't mind the starting drill as I have it down pat now. Thanks for all of the info. on the 426. I'm sure I can put it all together now and make it work. I'll be sure to keep several plugs handy. I have a 6yr old son that loves to tweek the throttle as he walks by. :ugg:

camrider · Feb 18, 2004

One new Plug and the beast fired up on the second kick!
I'll be sure to keep a few on hand for the trail and the track.

mxmatt426,
what's the difference between the CR8E (stock) and CR8EK?

That "glowing" headpipe is wicked. I'm glad that I had already found the posts stating that it was normal or I would have freaked and thought something was wrong.

mxmatt426 · Feb 18, 2004

Camrider,
The CR8EK has a double electrode, I think they last longer and ease starting, they do cost more, but it is worth it. How do you like that bike? The header is wicked, I was freaked out the first time I seen mine glow. If you have not already, do yourself a favor and change your coolant to engine ice, the 426 overheats quickly when they idle alot. Keep in touch.
Matt

camrider · Feb 19, 2004

I like it A LOT so far. I can't believe how powerful the bike is. I've been used to riding a older RM125 which is no comparison to the 426 - not even close.

I have'nt had much time to ride - yet. I noticed that it puked a little bit of coolant when I parked it in my shop after riding in my yard for only a few minutes. I assume/hope that this is normal?

I'll be changing all of the fluids as well as making any adjustments before I venture out onto the trail or track.

mxmatt426 · Feb 20, 2004

With regular anti-freeze they will puke it out. I use the Engine Ice, it is blue in color, and it retails for $16.99 for a half gallon. They even puke oil from the valve cover vent, when ran at high speeds (blow by). All of this is perfectly normal. I did notice, however, when I switched from Yamalube to Motorex 10W50, that the "blow by" slowed down.
Matt

Hick · Feb 20, 2004

camrider said:
I noticed that it puked a little bit of coolant when I parked it in my shop after riding in my yard for only a few minutes. I assume/hope that this is normal?

Probably. If you fill the radiators up to the neck it is guaranteed to have some overflow when it warms up. In my experience if you only fill to about 1/2" or so above the fins, or halfway to the filler neck, w/ the bike level, it will maintain that level (w/in reason) and won't overflow when it gets hot (w/in reason). You need to leave some room for the coolant to expand.

Matt90GT · Feb 21, 2004

Dont twist the throttle for sure.

If there is a pipe on the bike, you will need to jet the carb for sure.

Get a ZipTyRacing fuel screw ($15-20) there so you can adjust the fuel screw by just reading down there.

http://www.ziptyracing.com

For a jetting kit, get the JD unit. $65 or so for that from the store at http://www.thumpertalk.com

Once the carb is jetting and cleaned, you just have to learn when to use the choke and when to use the hot start. That is really the key to starting them hot or cold.

My best advice to you is to install the YZ450F cam in place of the stock 426 exhaust cam. It has the autodecompression setup thus you can remove the decompression lever install a VibeGuy plug (thumpertalk member $10). and then be able to kick the bike like a 2 stroke! It really makes starting a no brainer. I can start the bike in 1-2 kicks cold without the choke with the above setups installed. No finding TDC, just kick!

Best money you will spend -- YZ450 cam!

camrider · Feb 22, 2004

I'm sure having the 450 cam is a little better/easier, but ever since I put a new plug in, the bike starts on the second kick every time. It starts on the first kick when it's up to operating temp., even without the hot start pulled.

Using the decomp. routine is not as big a problem for me. I have it down pat now. It was having a gas fouled plug that was the actual problem. I have a few plugs on hand now - just in case.

From what I hear, installing the ZipTyRacing fuel screw is well worth the $ and I plan to install one. As for me, the 450 cam is not worth the $ or the trouble installing it to get the bike started on one less kick.

mxmatt426 · Feb 22, 2004

The YZ450 cam will work in the 426, but the cam gear is different and it does cause the timing chain to wear out faster. Hot Cams makes a 426 cam with an auto decompression device that does not damage the timing chain. On the older 250F's the 2003 Yamaha exhaust cam will work with no problems. The adjustable fuel screw is very nice and a must have. I don't think jet kits are a must have, I installed a Yoshi system on my 426 and all I changed was the main jet, and it has more power than I can use.

Matt90GT · Feb 22, 2004

mxmatt426 said:
The YZ450 cam will work in the 426, but the cam gear is different and it does cause the timing chain to wear out faster. Hot Cams makes a 426 cam with an auto decompression device that does not damage the timing chain. On the older 250F's the 2003 Yamaha exhaust cam will work with no problems. The adjustable fuel screw is very nice and a must have. I don't think jet kits are a must have, I installed a Yoshi system on my 426 and all I changed was the main jet, and it has more power than I can use.

Do you have any proof of this "accelerated wear"? I would love to see some HARD data here.

Jet kits help mostly with the needles for the midrange.

Ride a bike with the 450 cam and you will eat your words about not getting one! Guarantee that one!

mxmatt426 · Feb 23, 2004

Matt90GT, I have a good friend with a YZ450F that I have spent a couple hours on (and started a few times) and it does start nice. I also have a 2003 YZ250F and it does start nice aswell. Yet, I still run the factory cam in my 2002 YZ426F because, Mr. Dubach said that the 450 cam does work, however the gear design is different and does increase the wear the chain. I will take his word for it. I race MX so I'm not really worried if it takes two more seconds to light the fire. As far as mid range power goes, have you ever rode a 426?

camrider · Feb 23, 2004

I personally can't see any reason to add any type of aftermarket parts to a 426 other than cosmetics (looks). The bikes are just furiously fast and have monster torque. Adding a part that makes an adjusment or the rideability of the bike easier, maybe.

If this bike was faster or pulled any harder in any part of the powerband, I would have to trade if off for a 250f. And I may have to anyway. :eek:

Matt90GT · Feb 23, 2004

mxmatt426 said:
Matt90GT, I have a good friend with a YZ450F that I have spent a couple hours on (and started a few times) and it does start nice. I also have a 2003 YZ250F and it does start nice aswell. Yet, I still run the factory cam in my 2002 YZ426F because, Mr. Dubach said that the 450 cam does work, however the gear design is different and does increase the wear the chain. I will take his word for it. I race MX so I'm not really worried if it takes two more seconds to light the fire. As far as mid range power goes, have you ever rode a 426?

This is my bike:

<img src="http://m.bobbitt.home.comcast.net/yz426fm/pics/side2.jpg>

You can see the list of mods here:

http://m.bobbitt.home.comcast.net/yz426fm/yz426fm.html

Any other questions about what I ride? And yes it does have the 450 cam. Personally on the 426 there is a lot of top end left there with some porting to be done.

For Doug, love to see the hard data. Everyone can say that the gear pitch is different, but where is the data to prove you get accelerated wear???????????????????????????

Matt90GT · Feb 23, 2004

Well since the pic did not work try this link:

http://m.bobbitt.home.comcast.net/yz426fm/pics/side2.jpg

http://m.bobbitt.home.comcast.net/yz426fm/yz426fm.html

camrider · Feb 23, 2004

Fess up Matt. Do you REALLY ride that bike or do you just tow it around on a trailor and show it off! :eek: :thumb:

That bike looks clean. It doesn't even have the normal rub marks on the upper frame, above the guards where your boots rub. Looks like you take care of your toys (as everyone should). I'm the same way. After a few rides, take it apart, wash, clean and polish. My wife calls it crazy. I call it insurance.

ockevin · Feb 11, 2005

your bike looks great....clean a$$

Scott Senatore · Feb 11, 2005

Hi Camrider,
I have a 00 426 and you are correct, they are cold blooded. My routine to start it is pull out the choke, 2 quick twists of the throttle ( when Cold ) and kick away, it will usually start the first or second kick. Hot, pull out the hot start, keep the throttle closed and kick, first kick just about every time. If you do drop the bike and have trouble starting it, pull in the compression release push the kill switch and kick it through a few time to clean it out, mine will usually fire right up. One more suggestion, the crank case breather will draw dirt up, as recommended by Rich I cut the breather hose close to the head (I did find dirt) and install a filter, mine is a small K&N type. For Oil I have run Mobile 1 15-50 with good results. Coolant I run Maxima collanol, I have only boiled once and that was a very humid day with a lot of idling (TonyD motocross school). Hope this helps.

Amadeus · Feb 18, 2005

When you guys are tryin' to start it according to the above protocol, do you guys have it in neutral with the clutch in?

Hick · Feb 18, 2005

Amadeus said:
When you guys are tryin' to start it according to the above protocol, do you guys have it in neutral with the clutch in?

If it is in neutral, why bother pulling in the clutch?

But (kick) starting just about any cold thumper in gear is going to be near impossible as the clutch will drag quite a bit until the oil and plates get warmed up.

Masterphil · Feb 20, 2005

GOD FORBID that we dont do what the ALMIGHTY DUBACH commands of us. Of course he says it wont work, that's one more reason for me to keep my older bike instead of buying a new 450. Can you really trust anyone who is in the pockets of any of the Big 4 (ktm, honda, yamaha, kawazuki)

Just install the 450 cam and forget the "drill". I too would like to see this "accelerated wear on the whatever and crap"

Another correction, The Oil vapor that comes out of the vent tube IS NOT blow-by. Blow-by is the oil that gets past the rings into the combustion chamber and is burnt, therefore expelled through the exhaust. The Oil vapor that comes out of the vent tube is simply that, oil vapor.

biglou · Feb 20, 2005

Yeah, that Dubach, he's one slippery character. :coocoo:

YZ426F cold start problem / question

camrider

Hick

jmics19067

mxmatt426

camrider

camrider

mxmatt426

camrider

mxmatt426

Hick

Matt90GT

camrider

mxmatt426

Matt90GT

mxmatt426

camrider

Matt90GT

Matt90GT

camrider

ockevin

Scott Senatore

Amadeus

Hick

Masterphil

DRN's Resident Lunatic

biglou

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