08 YZ450 Questions


20 replies to this topic
  • YZPaGuy

Posted March 07, 2011 - 04:29 PM

#1

I have an 08 YZ450F. I am racing harescrambles with it this year. The one thing I don't like about the bike is it loves to stall in the tights stuff. I am going to run it in the first three races as is then make some decisions. I am thinking a flywheel weight will help curb this problem?

I read a post about the GYTR 9.4 weight?

I am mechanincal but I am in no means a bike mechanic. Is this something I should try to tackel myself? What is involved.

Another thing is when it stalls sometimes it will fire right back up with 1 to 3 kicks. Other times I have to let it sit for at least 5 minutes before it will kick over. Why is this and how can I fix it?

Thanks for the help!

  • DPW

Posted March 07, 2011 - 05:30 PM

#2

very easy to install with the right tools,


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  • davcon

Posted March 07, 2011 - 06:42 PM

#3

I ride tight single track and have experienced the same as you. I installed the heaviest GYTR flywheel (9.21 oz) and a 52 tooth rear sprocket. As far as not wanting to start in those situations, (some will say it doesnt work for them but...) I kick it like a 2-stroke. Crack the throttle about a 1/4 and kick it hard thru the stroke. Usually fires right up.

  • spyr_409

Posted March 07, 2011 - 09:00 PM

#4

Maybe a rekluse

  • Jim813

Posted March 07, 2011 - 09:05 PM

#5

I ride tight single track and have experienced the same as you. I installed the heaviest GYTR flywheel (9.21 oz) and a 52 tooth rear sprocket. As far as not wanting to start in those situations, (some will say it doesnt work for them but...) I kick it like a 2-stroke. Crack the throttle about a 1/4 and kick it hard thru the stroke. Usually fires right up.


I find my bike starts better in neutral after a stall.

If in gear, I pull the hot start (and the clutch of course), no throttle, then use the kickstarter to bring the engine to the top of the compression stroke before giving a full kick (doesn't have to be fast, just full). Repeat as needed. It usually takes 1-4 kicks for me in gear, 1-2 if I take the time to put the bike in neutral.

  • ttr250dude

Posted March 07, 2011 - 09:38 PM

#6

I have the answer to all your questions.. lol
I also have a 2008 and ride wooded single track. I had the exact same problems you are having, stalling and hard to start after it stalled.
Here's what i did: Heavy GYTR flywheel, 52 tooth rear sprocket, stock 13 tooth front sprocket, and straight pump gas. This fixed the stalling 100%. I run a 165 main jet, 48 pilot, and fuel screw 2 1/4 turns out. Whenever i do stall it, i always use the hot start and she fires right up.

  • ttr250dude

Posted March 07, 2011 - 09:42 PM

#7

One more thing, these bikes hate dirty air filters. I find when my air filter is dirty it stalls more often. Clean it after every ride.

  • YZPaGuy

Posted March 08, 2011 - 04:31 PM

#8

So much good info! Thanks guys!

Jim, yes it definetely does start allot easier when in neutral.

have been practicing in some bad conditions the last few weeks. First week was 8 inches of snow to 10 inches of running water from the snow melting to 4 incehs of soup mud to solid ice all within 200 yards. Wipeouts were the norm. The second practice was sloppy and I mead sloppy mud. This last practice was just peanut butter mud. Sticky in one spot and like ice at the next corner. I don't usually stall that much but the last few weeks have been terrible. I am getting used to the bike and starting to find the flaws. The two above are the biggest right now.

TTR Dude, YOU FEEL MY PAIN! LOL What kind of power loss/changes did you notice with the flywheel? You said you rejetted. Was this to offset the flywheel change or other? Are you running an aftermarket pipe?

Last but not least, which motion pro fly wheel puller do I need. I looked at them on this site and want to make sure I order the right one. Looks like I will be tackling this before I race since the mods come so highly recomended.

Thanks for all the help! This site is awesome!

  • grayracer513

Posted March 08, 2011 - 04:42 PM

#9

What kind of power loss/changes did you notice with the flywheel?

There is no power loss with the flywheel, nor any other negative effect to running it. In fact, who will notice it very little except that your acceleration in poor traction will improve and the engine will start to pull smoothly at 1500 rpm slower than it used to at least.

  • DPW

Posted March 08, 2011 - 05:03 PM

#10

Last but not least, which motion pro fly wheel puller do I need. I looked at them on this site and want to make sure I order the right one.


http://www.motionpro...partno/08-0257/


Flywheel Puller, M24X1.5 R.H. Internal Thread

* Replaces Honda OEM tool 07AMC-MEBA100, Kawasaki OEM tool 57001-1565 and Suzuki OEM tool K5700-11565-LPT
* Includes 12mm crankshaft protector cap (OE tool 07AMC-MEBA110)
* Fits Honda CRF 450R 02-07, CRF250R/CRF250X 03-07, CRF150R 07-08, Kawasaki KX 250F 04-05, KX 450F 06, Suzuki RM-Z 250 04-06, RM-Z 450 05-06, Yamaha YZ 450F 06-07

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  • ttr250dude

Posted March 08, 2011 - 05:22 PM

#11

TTR Dude, YOU FEEL MY PAIN! LOL What kind of power loss/changes did you notice with the flywheel? You said you rejetted. Was this to offset the flywheel change or other? Are you running an aftermarket pipe?


Yes, much pain haha, but its all good now. The only difference with the heavier flywheel is less wheel spin and I can lug the engine through tight corners without stalling. There is no noticeable decrease in throttle response. Like Gray, i think this should've came on the bike from the factory.
As for jetting, this has nothing to do with the flywheel. That jetting is simply works best for me. All of my exhaust is stock other than a Lexx endcap. I haven't ridden with the Lexx endcap yet but im gonna throw in a 168 main and turn my fuel screw 2 1/2 turns out.

  • YZPaGuy

Posted March 08, 2011 - 05:29 PM

#12

Nice, thanks for all the great info. Any tips, other then the puller, for me? Also any other easy mads that will make her better?

  • ttr250dude

Posted March 08, 2011 - 05:50 PM

#13

Also any other easy mads that will make her better?


The stock muffler is really restrictive. An aftermarket muffler or PMB or Lexx endcap reallys wakes up the mid range alot. I got my Lexx endcap brand new on ebay for $94 shipped. I think its carbon fiber look looks alot better than the billet from PMB. The Lexx is cheaper than the PMB, and unlike the PMB it comes with a spark arrester, silencer, and 2 different outlet sizes. Fit and finish is top notch. Lexx all the way.

  • YZPaGuy

Posted March 17, 2011 - 06:46 PM

#14

I'm on my way! I installed the flywheel today. It was really easy and that puller worked great. Tomorrow the 165 main and 48 pilot goes in and I am going to change the rear sproket. I am going to order the Lexx exhaust silencer for $170 to my door. Going to test it Saturday with just the sproket, flywheel and jets. I will post a report.

  • ttr250dude

Posted March 18, 2011 - 01:13 AM

#15

I am going to order the Lexx exhaust silencer for $170 to my door


No need for the full muffler. This is what i was talking about. The endcap alone will really open up the exhaust flow.
http://compare.ebay....4=263602_304662

  • Gunner354

Posted March 18, 2011 - 04:55 AM

#16

No need for the full muffler. This is what i was talking about. The endcap alone will really open up the exhaust flow.
http://compare.ebay....4=263602_304662


Sorry but you need to do some more research. The stock exhaust kills 5hp. The end cap has nothing to do with gaining power. Spend the money on an aftermarket exhaust and you will be greatly rewarded

  • grayracer513

Posted March 18, 2011 - 07:00 AM

#17

Sorry but you need to do some more research. The stock exhaust kills 5hp. The end cap has nothing to do with gaining power. Spend the money on an aftermarket exhaust and you will be greatly rewarded

The end cap kits actually do have something to do with power output on the '08-'09 models, as they eliminate one of the two restrictive cones in the pipe. You can remove both, but the muffler is a bit loud like that due to its length.

The cap kits are a low cost option that do make at least their money's worth of an improvement, and also make a spark arrestor available. A full slip-on, or better, a full system is the best choice if the optimum performance is what you're after.

  • Gunner354

Posted March 18, 2011 - 11:32 AM

#18

The end cap kits actually do have something to do with power output on the '08-'09 models, as they eliminate one of the two restrictive cones in the pipe. You can remove both, but the muffler is a bit loud like that due to its length.

The cap kits are a low cost option that do make at least their money's worth of an improvement, and also make a spark arrestor available. A full slip-on, or better, a full system is the best choice if the optimum performance is what you're after.


Have any dyno charts on that. Pretty sure the internals are the root of the hp loss and not the end cap.

  • grayracer513

Posted March 18, 2011 - 12:48 PM

#19

One of the two cones is built into the OEM end cap, so it goes away to begin with. The other can be removed at the same time. Anecdotal reports from actual users is all I have to go on at this point.

  • Gunner354

Posted March 18, 2011 - 03:40 PM

#20

Sounds reasonable





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