Mid-range bog

Post by **Matt** » Sun Jul 31, 2005 9:17 pm

Ever since I rebuilt the motor in my 400, it has not run quite right on the ground. On the lift, it seems fine. It idles perfect. When I want to get moving, it bogs and won't budge until I get the throttle to about 3/4, then it revs up and takes off. It won't do anything between idle and 3/4 throttle.

Any suggestions on where to start with this problem? My first instinct is that I did somthing wrong in the motor's timing, but it runs perfect except in that mid range, so I'm not sure about that. I'm thinking that it may be a clutch problem, which would explain why the problem doesen't occur until it is on the ground. Perhaps is it fully closing way to soon. The secondary is in the correct position to start out.

Discuss.

wadeo108 · Post by **wadeo108** » Mon Aug 01, 2005 8:34 pm

check to see if the secondary is opening to soon. if the belt is getting sucked it to the secondary it would not take off.

Deere Daze · Post by **Deere Daze** » Mon Aug 01, 2005 10:48 pm

Matt...
Did you do anything with the carb when you rebuilt the engine.. if so the high speed needle could be set to lean..Ed

Rodimus Prime · Post by **Rodimus Prime** » Wed Aug 03, 2005 1:27 am

340/5 engine with walbro carb and points ignition..

if compression is good on both sides and you have no air leaks anywhere it should be crusing at just off 1/4 throttle around 15 mph.

you could a) be running on one clyinder only bad sparkplug or miss firing at wrong time.

B) your primary clutch spring is toast or close to.. with clutch on ground a good spring in it should require one to almost jump on clutch to get it to move.

dont suppose you could tell us at what rpm the clutch engages and wheater or not the belt spins on primary or secondary instead of moving sled.?

my guess is it is something you overlooked since you already know alot about theses sleds.

Post by **Matt** » Wed Aug 03, 2005 11:11 am

After reading your comments, I just fired it up on the lift with hood up and console off. By 1/4 throttle everything is rolling and the belt is already shifted halfway between the clutches. This doesen't seem right does it?

Unforunately the speedo isn't working and it has no tach, so I can't go by them. I think I'm going to try a different primary, as I've never done any work on the ole Salsbury.

Post by **Matt** » Wed Aug 03, 2005 12:00 pm

I switched to a spare 101, and the movement looks to be the same. I put the salsbury back on and took it for a spin around the yard.

Here is what happens when I give it light throttle: The clutch starts to engauge and the sled starts moving. Then the motor bogs, the clutch disengauges. If I stay on the throttle, it will then spin back up, clutch engauges, and it takes off. I was working with the carb as I was starting and stoping. It was getting better and worse as I adjusted, but I couldn't find a happy spot.

Think I should go through the carb again?

Deere Daze · Post by **Deere Daze** » Wed Aug 03, 2005 9:05 pm

Matt
Sounds like the carb may need to be rebuilt.The walbro carb, if its been used, and sits on its back or upside down,and then dries ,the metering diaphragm can dry and distort into anything but a flat surface and that will cause the problems you are having.Best thing to do is to rebuild the carb.One more thing to check would be if the motor is to far forward.Ed

Deleted User · Post by **Deleted User** » Thu Aug 04, 2005 8:21 am

Sounds like it is running normal for a motor that is tuned to run in the cold. I just had my old invader out around the yard and it was a bit boggy also. To much gas to little air. I dont know about anyone else on this sight, but I have never had any luck tunning a sled in the summer, and having it perform good in the winter. If it was me, I would not worry to much about the performance until it gets cold out. My 2 cents.

Post by **Matt** » Thu Aug 04, 2005 5:02 pm

Unforuantely, this is not just a summer problem. It does the same thing when the snow is flying.

JDGuy · Post by **JDGuy** » Fri Aug 05, 2005 4:34 pm

Hi Matt:

At a distance of some 800 miles or more from your situation, it sounds to me like it may be that the secondary clutch is upshifting way too soon, especially since you tried two different primaries with the same result. Wrong or weak secondary spring, maybe wrong helix??? Sounds like a vehicle with a 4 speed manual, if you shift into 4th at 15 MPH and hit the throttle, you will get a "bog" until you get to 60 mph or so. Try some new parts, especially the spring, in the secondary. Good luck. That is my 2 cents worth. They say an "expert" can be anyone 50 miles or more away from the problem

THANKS FOR ALL YOU DO TO KEEP THIS SITE GOING!!!

Mac67 · Post by **Mac67** » Wed Sep 14, 2005 11:20 pm

hey mat , my brother 500 was having the same problem with a walbro carb , instead of rebuilding it we swiped an intake from aspitfire and ran a mikuni slide carb on it and solved the problem , and thanks for the site