416-8 Acceleration Problem

[richm1386 2]

I tried looking for this in the forums for about an hour and came up empty so here goes.

 

My dad gave me his old '89 416-8 with twin Onan engine and 42" reat discharge deck. It's in pretty good shape and runs fairly well aside from the surging problem. My issue is when it takes off. Unless you are extremely careful with the clutch pedal, it does a wheelie in every gear but reverse (obviously) and takes off like a rocket. If you pop of the clutch in 3rd it feels like it's going to tip. I've driven this thing since I was about 12 and didn't always do this. I remember maybe 10 or 15 years ago my dad had work done on it and that's when it started. Then in maybe the past 5 years he rebuilt the transmission and I got much worse.

 

I already checked to make sure the brake wasn't catching and I adjusted the reunion on the clutch pedal to give myself some more control in the pedal travel. I also found the damper piston behind the tensioner belt and adjusted that out to slow down the rengagement of the belt but none of seemed to work. And maybe this was a bad idea but I stretched the clutch tension spring a little because I thought that might loosen things up. 

 

I think what's happening is when you let off the clutch the belt doesn't grab the axle pulley gradually to start you moving. Instead it gets a full grip all at once and jerks you forward. The only other thing I could think of is the belt on it is wrong. I dont know if it's an OEM but it seems to fit fine. I dont see any markings on it but the top and bottom of it are green if that helps. 

 

I'll take any advice you guys have. I already ran into the garage door once by mistake because of this problem. Now my wife thinks the tractor is a death trap and I'm running out of garage doors.

[ericj 1,578]

try a factory OEM belt. I have several 416-8 with the onan motor and none of mine are that severe, unless you pop the clutch in 3 rd gear with a wide open throttle. The belt should be either white or black. A green or blue belt are after market. Sometimes you can get away with running those, but since you are having problems I would recommend the OEM belt. good luck

 

 

 

 

 

 

eric j

Edited April 9, 2019 by ericj

[JoeM 7,874]

Like eric says, the OEM belts are the best fit and are the correct rubber and or wrap configuration. Your machine uses a Toro 93-9809 (replaces 107939).

Something that is critical is the belt cover. It has slides that act like guides and hold the belt up allowing the "clutching action". If the cover is not installed correct or the guides are to low or missing (part #5 on the second drawing) it will grab. You can look under the machine and see the belt lay on the guides when the pedal is depressed. Also, there small wire guides (#14 and #17 on the first drawing) at mount to the engine that keep the belt close but not touching the pulley when disengaged. These wires should just be off of the belt when the clutch pedal is out. Make sure both pulleys are not rusted or dirty, and the idlers is in good shape free to turn, this causes grab too. I see you may have tried this one, if you can adjust the pedal so the clutch disengages closer to the floor this gives more control than having it grab at the end of the travel where you have less control to manage the feel of engagement. I rarely engage the clutch when at full throttle, Pretty much have it running at low rpm and rev it up after I get going.

Hope this helps.

[ebinmaine 68,389]

 to 

 

 

I'd start with the belt as well.

Is your belt guard in place and not damaged?

Is your belt a cloth-covered machinery type?

A standard rubber auto belt won't work.

 

I've had good luck with Gates green belts but lots of other folks ONLY run OE for the reason you're having.

Also, check to be sure the pulley system doesn't have any rust. A rusty pulley will grab hard. Also a cracked or chipped one.

 

Reassure your wife that the tractor is NOT a deathtrap.

Once the issue is repaired you have one fine piece of American quality.

 

[Racinbob 11,232]

Wheel Horse utilized different methods to help control this. There was a hydraulic damper that rode with the idler arm throughout the travel, a pressurized strut that did all the work and didn't utilize the 108035 spring, and a damper that just caught the idler arm at it's reward travel. That last one is what you have. I had the first type mentioned when I got my 2005. I didn't realize what was going on at first but I knew I didn't like it. I'm betting your damper has pooped out and between that and the belt you have this problem.  For decades just the spring on the left side worked fine. I would suggest that you remove the damper, make sure all the pulleys are in good shape as well as the spring and then install a new belt. While others will work I always use a Toro OEM belt on the drive. Then I know it will be fine. Once I got my 2005 'converted' back to the good old style set up I love it. 

[bds1984 1,444]

I had this problem about fifteen years ago on my C165.  I made the mistake of releasing the clutch too soon, the front end came up, and the seat and I went tumbling off the back!

[richm1386 2]

Thanks all. I guess I've got some more work to do this weekend. I also know I should throttle down when changing gear but it usually wants to stall out when I do. I'll have to mess with that too.

[ebinmaine 68,389]

4 minutes ago, richm1386 said:

changing gear

not sure what you're doing there one way or the other but you should never ever ever change gears when you're moving.

 

These Transmissions have square cut gears and they are not synchronized.

 

 

You'll definitely get it figured out. Just a matter of narrowing things down one by one by one.

[richm1386 2]

No I've made that mistake before. It's not a good sound. What I mean is I press the clutch pedal, come to a complete stop, then shift, then release the clutch as slowly as I can to avoid the while wheelie problem. What I dont ever do is throttle down the engine during that operation because it starts to stall out if I do. 

[wallfish 17,080]

Check the pulley grooves as well. Mainly the engine drive pulley. If they are rust covered or if they were painted, that could cause the sudden engagement of the belt. .