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04 800 rev PROBLEM CHILD

S

swrev

Well-known member
Jun 26, 2008
952
349
63
Lewistown, MT
You probably dont want to hear what I think it is:confused: I think the crank might be on its way out. Maybe a bearing. Mine did the same thing. How many miles?

Mine is having similiar problems, around 5000 miles total, 500 on top end. Did you ever take the belt off and rev, did it fluctuate? My Rev doesnt
miss a beat if I try that, just curious.

Mine ran great last year. Would recover track speed and r's if it ever bogged. I can only hit 7800-7900 RPM since first ride of season, would like to see 8000-8150 inititially when hammering it. I've cleaned, inspected clutches, installed new springs. No help. Also tried a different pipe and can-nothing. Tested DPM solendoid last night, works great, o-rings look good. I've even checked/changed plugs and belt.

The only real change from last year is my oil delete. Could that be causing a problem? I am going to check my throttle linkage tomorrow and make sure everything is opening up.

Beyond that, I'll ride til she blows I guess
 
R
Nov 8, 2009
37
11
8
Ran it today with 19.8 grams. Same problem. The only difference is the RPMs are now surging between 7600-7900 vs 7700-8000.
Van Epps, Put in 360 mains,needles on 3,160/350 primary spring,15gms of total pin weight,clickers on 4,and fresh 91 octane fuel without any additives or race gas. Keep the 19/45 gearing. Start with this as a baseline. Watch your EGTs and rpms on the trail!
 
V
Jan 3, 2008
786
105
43
Eastern Wshington
Revsum, I don't have EGT's. I know I need to do this asap as I'm now thinking I must be down on power, possibly due to some overheating?

Tonight I put my setup back to the way it was when I bought the sled and it was running very good.

19/43 gearing
Straight 44 helix
double purple secondary spring (anyone know the spring weights of this one?)
yellow primary spring (this one to?)

I also dropped the mains to 380's, went through the carbs again and synced them. Had the raves gone over by a good DOO mech.


Tested it at 9:30 tonight (wife's not real happy:eek::D) and it still does the SAME THING!

Im thinking maybe Im down on power with my lowish compression numbers and 9lbs difference between cylinders. I guess I need to tear it down and look over the jugs / pistons real close????
 

Stuck

Well-known member
Premium Member
Feb 4, 2002
279
61
28
Bridger, MT
So have you done a burn check to see if you are running lean? If you have modified the air box, there is a chance that you could be running lean. Heck you could even just throw in some bigger jets to see if it makes a difference. I saw that you just dropped from 390's to 380's. Maybe try something bigger?
 
V
Jan 3, 2008
786
105
43
Eastern Wshington
Tried 400 mains ........ no difference
checked timing and its good
split airbox to check for alterations .... it's stock w/ no changes

the symptoms are getting worse. Initially surged between 7500 to 7800 or so
after 6 rides or so the surge range dropped to 7400 to 7600

last ride it was surging from around 7200 to 7600. (with 400 mains) Also during this ride it would intermittently not surge at all and top out at 6800 flat~! Just a total turd on top.

a partial list of things tried so far:

tried 400, 390, 380 mains
been through carbs 3 times
synced carbs
new fuel filter
been through raves 3 time
been through reeds 2 times
split air box to check for internal modifications
been through primary and secondary 2 times
new dpm
checked timing
ohm checks of stator, coil
check crank for phase
checked pipe for cracks
swapped mpem / tether
swapped exhaust can
BJ clutch set up
Al clutch set up
went back to running original gearing and clutching that used to rip
new belts, plugs

any more ideas guys? Starting to think this is a tiny electrical gremlin
 
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V
Jan 3, 2008
786
105
43
Eastern Wshington
No, but the dealer just swapped out the fuel filter and didnt say anything about that. I think it would have been obvious as the filter is in the tank.

But, I think I know what it is.... I think I have a short in the kill switch circuit. If that proves to be true.................... lets just put is this way, I almost hope that's not the problem!!?? Have to wait till Wednesday to have the shop check it out.
 
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B
Dec 21, 2009
11
0
1
Wow Van Epps these revs are killin us!
Here's my latest rundown:
Fresh rebuilt motor popped with 285 miles. Took it apart mag piston popped destroyed the cylinder and head. Carnage fell into the also freshly rebuilt bottom so I took it apart also just to be sure it was OK. Found out the guy that rebuilt the bottom used the wrong bearings and now the crank is also pooched!
Still love riding this sled so decided a shortblock is the answer. Put it all back together still getting the bog 10% of the time. When it does'nt bog it's pulling 8100 rpm solid. Checked the plugs and they looked a little light so put 400 jets back in. Plugs look a little better now. Going to put the stock reed spacers and rave springs back in and will be 100% stock again. Find out this weekend if it gets better. Cleaned DPM again and checked/cleaned carbs again. This thing is killing me and my wallet!
Help!!
 
V
Jan 3, 2008
786
105
43
Eastern Wshington
Brute,

Sorry to hear about your money pit~! Hope the guy that did the rebuild steps up. I hear you about the money.........I'm just about over it...

I'll definitely let you know what my problem is once I FIND IT:clock: Just a matter of time. (and money:face-icon-small-fro)
 

live2beel

Well-known member
Lifetime Membership
Nov 26, 2007
1,138
475
83
Have you tried unplugging the main harness to the kill switch and hand warmers.
 
S

swrev

Well-known member
Jun 26, 2008
952
349
63
Lewistown, MT
Found the problem w/ mine finally. The rod on the pto side went out along with many other parts. Hopefully yours is not having the same thing happening. I had mine tore apart a week before to put in new pistons, and didn't notice anything at the time. Only went 80 more miles. Looks like a good excuse now to speak w/ BJ.

Good luck with yours Van Epps
 
D
Dec 11, 2008
598
54
28
Livingston MT
Ok mine does the same thing. but when i put my clickers on one it stops. and also i had a dealer tell me that running too rich can cause it to not run smooth on the top end. check your plugs after keeping it floored till it stops. also if you know anyone else with your style rev try swaping out primarys and if that dont do it try swaping secondarys.
 
T
Nov 28, 2007
145
5
18
44
seymour b.c
Wow Van Epps these revs are killin us!
Here's my latest rundown:
Fresh rebuilt motor popped with 285 miles. Took it apart mag piston popped destroyed the cylinder and head. Carnage fell into the also freshly rebuilt bottom so I took it apart also just to be sure it was OK. Found out the guy that rebuilt the bottom used the wrong bearings and now the crank is also pooched!
Still love riding this sled so decided a shortblock is the answer. Put it all back together still getting the bog 10% of the time. When it does'nt bog it's pulling 8100 rpm solid. Checked the plugs and they looked a little light so put 400 jets back in. Plugs look a little better now. Going to put the stock reed spacers and rave springs back in and will be 100% stock again. Find out this weekend if it gets better. Cleaned DPM again and checked/cleaned carbs again. This thing is killing me and my wallet!
Help!!

what does the bog feel like, does it seem like it is losing spark in one cylinder and when you let off it will come back after it idles down, if thats the case you are detonating and a ring is sticking causing a loss of compression, after it cools slightly it frees and comes back to life. did your piston have the 4 corner seizure and is it black on the inside of the piston on the top.
 
B
Dec 21, 2009
11
0
1
Actually when it burnt up, the mag side leaned out and melted down the piston on the exhaust side. ripped one of the rings apart into pieces. pretty sure the chunck of ring is what destroyed everything inside. PTO side looked good other than a little detonation or scavenging through the y pipe. Stock reed spacers and rave springs back in now. Rode it last weekend and it ran like a champ till I ran out of fuel! Back to the mountains in a week lets hope it runs good!
 
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