Heavy flywheel on an EXC450

[Harvey Mushman]

I just bought an '04 EXC450 with a plate. I bought it from the original owner and have known him for some time. I was surprised when he bought it new, he told me he put an aftermarket heavy FWW on it, said he had problems with it stalling too easy. This seemed to fix his problem. I've put heavy wheels on my 300's in the past but I never thought a 450 EXC needed one. I've only ridden the bike for probably 40 miles so far but can see the logic in it. Gear changes are noticeably smoother on the street I think because the RPM's don;t drop so quick when shifting. It's very subtle but it makes a difference. On my '03 450, I seemed to have to make a concious effort to shift quickly and feed throttle back in precisely when letting out the clutch. If I shifted it "lazy" like my Lc4, it would get jerky. The lack of cush drive exacerbates this but I didn't notice this on the '04 bike. Off road the bike seems to lug better than the '03. You can let the revs get down lower on the '04 without a bunch of chain snatch than what I remember on the '03. Gearing is/was the same on both the '03 and '04. The bike will still snap the front wheel up easily in 1st gear so the FWW didn;t kill the power, just smooths it out abit. Overall, I think the FWW makes the bike just a bit more "civil" and demands a little less commitment from the rider, both on and offroad. Thought this data may be of value to some. YMMV.
Happy holidays ....

-Harvey

'04 EXC450
'02 EXC300
'98 RXCe620

[Hayden]

Do you loose any snappyness because of the heavy flywheel. It probably doesnt rev up as fast does it? Or does the 450 have enough umph to not notice it much? I think this would tame down my 650R a bit on the street if I did this. My shifts on the XR are a bit jerky when street riding.

Hayden

[Harvey Mushman]

I couldn't tell you for sure as I've only put about 40 miles on it. I'm still getting the AP dialed because it has the "standard EXC bog" right off idle. Once you get thru the bog it hits with authority so I know the power is there. So far I liked how it smoothed out the shifting and helped it lug better. I went from a 42 to a 45 pilot, went to the 4th position on the needle, about 2 turns out on the fuel screw and put a different diaphram in the AP. This is basically what I did to the '03 I had and it ran really well. By that time it was 9;30 PM last night, I was tired and didn;t ride it. It started will and responded well on the stand. I may still o-ring the AP linkage. Hopefully we get some semi-decent weather soon and I can ride it. I'll report back what I find.

-Harvey

[Savage]

Let's see a pic of'er.

[Harvey Mushman]

http://ktmtalk.com/index.php?s=0d046bf0 ... pic=180932

After I rejetted the carb and swapped AP diaprams earlier this week I couldn;t understand why it had such a bad bog right off idle. It was worse than it should have been. I got to thinking, could I have installed the AP diaphram in upside down?, (the rivet should face down). I took it apart yesterday and sure enough, I had it in upside down. I turned it around and went for a ride. Noticeably better, but I'm still not quite satisfied with it. I'm going to play with the AP squirt timing and o-ring the linkage next. Now, more on the flywheel. My son and law (on his YZ250) and I did about 25 miles of single track at the river yesterday afternoon. One thing I never cared for on a 4T in the woods was the compression braking. The FWW makes a BIG difference in the lack of compression braking it now has. Not quite like a 2T but considerably less which keeps you from tiring out as fast. I now do thnk the FWW takes a bit of the power away on the street but it's not much. Personally, I soft pedal it on the street as I try to save the rear tire for the trail so this compromise doesn;t bother me. The fact that it lugs better, has less compression braking, and is overall smoother on & off-road is well worth the trade off to me. The FWW probably wouldn;t affect the power of Haydens XR650R or an EXC525. The 450 is evolving into a pretty cool little trail bike and the best thing is it's street legal. I posted the link to the FCR jetting parameters on KTM talk above. There is some good info in there. You may have to register on the site to access it.

Take care

=Harvey

[slimtrader]

Just let me know when you have it all straightened out and running right so I can buy it from you!