Need some advice from 450 owners and yz450 guys

[rosscopeeko]

Ok, so i've got a riding budy who just got back into riding by purchasing a new 06 yz450f. He broke it in fairly hard. For example, with only 2.5 hours on it he was climbing nasty hills in our area at wide open throttle. I'd say the bike has 15-20 hours on it now. Anyways, the bike has always been hard to start. It also stalls all the time. For example, i rode it and was blasting through the gears and as soon as you pull in the clutch to coast it dies. Is this normal? Also, the bike is now starting to backfire on long hill climbs and sounds different. It reminds me of a volskwagon bug pinned and reving out. We were at these long sand hill climbs where there were new rm450's and crf450's and my friends yz450 didn't sound the same. I keep telling him to check the valves but he's been avoiding it. He has a racer contact in town who's telling him that he won't need to adjust the valves if he doesn't redline it, but i know my friend has ridden the snot out of the motor on these nasty hills. What do you think? He was running 94 octane fuel with octane booster, stock jetting, does regular oil filter cleanings and oil changes. I need some advice from you 4 stroke guys before he fries his motor. Thanks

 

[sick 96 250]

it could just be the jetting

 

[Matt90GT]

you know the break in thing, that is more than enough. I get 2 heat cycles in the bike (ie on the stand for 3 minutes at fast idle) and then ride it like normal.

Sounds like you have a clogged pilot jet. With the 06 450s, installing a larger 48 pilot will help a lot of the running of the bike.

 

[Mophuka]

my buddy has the same bike with the same problems, he adjusted the mixture screw and that helped the backfiring. i heard they run a little lean from the factory. as for the stalling, that also happens. he could add a flywheel weight and that could help..

 

[fizzle]

Have him drain the gas tank, and try straight premium pump gas without the octane booster. My YZ 450 had all kinds of problems, seemed like valves or carb, but at the end of the day, it was due to the fact that the octane booster was hosing up the air/fuel mixture. You shouldn't have to run octane booster in a stock engine.
As far as the backfiring goes....mine backfires whenever I let off the throttle, apparently that is normal for the YZ.
Your friend will have to adjust the valves at some point, regardless of the revs he runs it at, or risk piling up the engine when a valve snaps off and drops into the cylinder.

 

[Matt90GT]

install a 48 pilot. It helps the bike a ton, and will solve the popping on decel.

Also get an extended fuel screw and get it adjusted.

 

[BSWIFT]

Have the exhaust gases analysed. It only takes a few minutes and will diagnose the lean/rich issue. The Fly Racing T-handle fuel screw is a must and raise the idle slightly. To start, use on stab of full throtle when cold and that should help. The stalling is due to the lack of flywheel weight. Definitely check the valve clearances it only takes a few minutes and is worth the time.

 

[Matt90GT]

stalling has nothing to do with flywheel weight. it is all about jetting

 

[Okiewan]

stalling has nothing to do with flywheel weight. it is all about jetting

Wrong.

 

[Sawblade]

Raising the idle will also help with the stalling and adding a adjustable fuel screw should eliminate your problems. If adjusting the fuel screw doesn't do the trick, you will need to replace the pilot jet.

 

[Matt90GT]

Wrong.

Oh ok.

THere are many circuits to the FCR carb. You have to get them all dialed in. I have no bog issues or stalling. Add some idle to the bike and you wont have stalling issues.

Most of the time people have stalling issues cause the carb has the off idle bog. Solve that and life is MUCH better.

 

[rosscopeeko]

Thanks for all the good info guys. I'll forward this post to my friend. He was talking about how he heard boyesen makes an accelerator pump upgrade for the carb and that it might help his problems. His bike backfires on heavy load while climbing huge narly hills. It also sounds different from other 450's, like it might be missing a little at high rpm's. He's going to try running just straight premium 94 octane. He's also going to buy a jd jetting kit i think. When do you think he should check the valves? Thanks again for all the good info.

 

[Okiewan]

Oh ok.

What was wrong was saying stalling has nothing to do with flywheel mass. A heavier weight WILL reduce stalling.

 

[Ol'89r]

I keep telling him to check the valves but he's been avoiding it. He has a racer contact in town who's telling him that he won't need to adjust the valves if he doesn't redline it,

Adjusting the valves is the first thing he should have done. IMO.

Tight valves will cause the conditions that you describe. Running a 4s with tight valves will burn the valves and seats and do costly damage. I really don't understand why people avoid checking their valves until they have damaged their engines. It's not rocket surgery or nuthin'. :coocoo: Your buddies racing friend is wrong. The valves in a new engine can tighten up in just a few hours regardless of the rpm range used.

A flywheel weight will most definitely help with stalling especially on tighter trails.

Cleaning the carb and making sure there is no dirt or water in the float bowl and accelerator pump area would be a good idea before changing any jetting. Also, go back to the 94 octane gas. Running a octane booster or oxygenated fuel can affect jetting.

Once you have checked all of these other things then fine tune the jetting. If the bike ran good at first, it's probably not the jetting. Jetting doesn't change by itself.

Just my $ .02

 

[RCJ81]

Adjusting the valves is the first thing he should have done. IMO.

Tight valves will cause the conditions that you describe. Running a 4s with tight valves will burn the valves and seats and do costly damage. I really don't understand why people avoid checking their valves until they have damaged their engines. It's not rocket surgery or nuthin'. :coocoo: Your buddies racing friend is wrong. The valves in a new engine can tighten up in just a few hours regardless of the rpm range used.

A flywheel weight will most definitely help with stalling especially on tighter trails.

Cleaning the carb and making sure there is no dirt or water in the float bowl and accelerator pump area would be a good idea before changing any jetting. Also, go back to the 94 octane gas. Running a octane booster or oxygenated fuel can affect jetting.

Once you have checked all of these other things then fine tune the jetting. If the bike ran good at first, it's probably not the jetting. Jetting doesn't change by itself.

Just my $ .02

Couldnt agree more. Tell your buddy to start saving his money now. He keeps riding it like that they will soon be parted.