Odd little question regarding 671 and Clutch under load.

zubzub · October 11, 2007, 10:36:09 AM

When I went to try out my 4104, it was parked on a fairly steep hill, facing up, and the rears had sunk in a little.(8"?). So I had to rock it out. Now my question, (from someone who had never driven a DD 2 stroke before). As I was trying to get it out of the hole, at full throttle the engine revved up and down, in a very regular way, like a governor was coming on and off( aprox on/off 1Xper sec.). Now this is what i thought, but the other thought was that the clutch was slipping (but I figure that would be a total slip not on and off). So, is this regular and if not what do you think the problem is. BTW once I was out of the sunken in part it did not do that again I was still on the hill, no problem. As always thank you in advance fro any thoughts, input, etc... Patrick

HB of CJ · October 11, 2007, 02:37:04 PM

Not exactly sure what you mean, but we think we have enough info to help you out. Sounds like your governor is trying to add MORE fuel to the mill AT IDLE to compensate for the rpm loss BELOW idle when the clutch engages-with your foot OFF the throttle. Clear as mud?

Don't worry about it.

Also sounds like the governor may be a little bit worn as it delays events a little bit and combined with the clutch engaging, the mill sounds kinda like...."wrrummmp, wrrummp, wrrummp". This is a very common sound with a manual tranny 2-stroke Detroit, expecially when they are backing up....;

....starting off; or as in your case, rocking gently back and forth breaking the rear tires loose from like a hole, mud, ice, etc.. Most will tell you this is an abusive situation placing undue strain upon the driveline and they are correct as far as it goes. With practice, an operator can "time" out the surges.

Actually, letting the governor run the show (not the gas peddle) when backing up, rocking out, or starting up out of a hole is the preferred way of doing things, with just gently releasing the clutch. However, with older or worn equipment, it is usually impossible to do it SMOOTHLY. Carry on.

HB of CJ · October 11, 2007, 02:40:56 PM

Sorry ZubZub, I didn't read your question clearly. You said at full throttle. Let me think this one thru. Thanks.

gus · October 11, 2007, 08:11:36 PM

The full throttle part kind of got to me too. If this means you also had max rpm I don't see how you could have missed burning out the clutch.

However, I think you had full throttle but since it was both stuck and uphill you probably were not getting anywhere near full rpm and the engine was lugging down to almost stopping then surging as the load was released.

You can't get full rpm from an uphill dead stop in a 4104 with the clutch fully engaged, you can just barely keep it from stalling. Don't ask me how I know all this!!

I assume you know not to use the foot throttle when starting a 4104 from a dead stop, always start it from idle or risk a burned out clutch. Sometimes (Uphill) it is not possible to keep from adding a little throttle and using a very slight clutch slip but it should be avoided if at all possible. It would be nice if we had a good low first gear to avoid all this!

WEC4104 · October 11, 2007, 10:11:53 PM

I am also trying to interpret the comments and understand what is going on. When you say the engine was at full throttle do you mean the RPMs were up against the governor? (before letting the clutch out) Does the bus have a tach? If so what is the RPM reading?

Up at the rated governor RPM, I can't seem a clutch slippage problem creating a regular oscillation. That to me sounds more like a governor or fuel delivery issue.

zubzub · October 12, 2007, 12:54:10 AM

This only happened for a few moments. When it happened my foot was not on the clutch, but I did have the throttle floored. As it was not producing successful power for extracting itself during this oscillating, I used some other technique to get it out. I appreciate the comments about not using the clutch at full throttle, and I wasn't, but there was no way I was getting out of there without burning a litle clutch.
As i am a novice with this engine it is possible I floored it under load when it was perhaps at 1/2 it's governed rpms (although it sounded full speed to me). Is this a problem? Would seem like a usual technique on the highway, getting the max out of the engine.
Finally I will be checking the governed max speed/ no load, so that i know what that sounds like and so I can assure myself that it is around where it should be. How /what do you attach to the motor to have a tach? And is it rentable/buyable?
Thanks to everyone, Patrick.

Don4107 · October 12, 2007, 08:41:23 AM

Patrick, a couple suggestions.

When the tires are sunk, dig it out first, all four corners. You can make it a bunch easier on the drive train if you dig ramps for the tires to roll up. Instead of starting out uphill back up, downhill, out of the holes first if conditions allow.

If you had your foot off the clutch with the throttle floored with the engine at max RPM and you where not going close to 15 MPH or spinning the drivers you where slipping something. Will the clutch hold in 4th gear with the throttle floored from about 45mph to max speed? If not, time to look at the clutch.

Good luck
Don 4107

zubzub · October 12, 2007, 09:02:32 AM

Well I got it out of the hole, I'm Canadian, I know how to unstuck things. My concern/interest was the oscillating of the engine under load. It was an extreme situation with an inexperiaenced driver so maybe it will never happen again. I asked the ? because I thought this was something common that either indicated a problem or was not a problem. I asked the question at the DD yahoo site, there is a guy there diagnosing a bus with a similiar problem, maybe he will work it out (bus cruises to 60 mph and then the governor? starts oscialating the engine.

zubzub · October 12, 2007, 04:10:28 PM

ok I worked a way to describe it. it sounded like the bandag bullet at idle

http://www.youtube.com/watch?v=haA_RR1_K4g.

very regular. maybe I was bogging down the engine and that made the sound

gus · October 12, 2007, 06:23:49 PM

If the clutch is not slipping you can floor the foot throttle under full load all you want with this setup but nothing will happen except excess fuel flow and engine lugging. This engine will not develop high rpm at rest or barely moving. As already said, it takes at least 10-15mph for high rpm in first gear.

The rpm oscillating was the engine choking on fuel and trying to quit.

Keep in mind that this is a high rpm engine compared to the large Cummins or Cat truck engines. It develops very little power under1600 rpm and must be wound to the governor (2125-2150rpm) when going through the gears.

60 mph is about all you will get out of a 4104 unless you mess with the gov or are going downhill! At that speed the governor is just about maxed out. I use 60mph as my cruising speed. It will go a bit faster but the engine doesn't like it based on the vibes it sends to me!!

I'm in no hurry-I'm enjoying the scenery and driving my bus.

PS. What the heck is a bandag bullet??

zubzub · October 12, 2007, 10:59:25 PM

Like I said I really don't know this powertrain at all. SoI guess I was just making it do what it didn't want to do.
Gus, the Bandag Bullet is a truck with some kind of 16V diesel engine. Kind of foolish, check the link and there are other clips at youtube if you put bandag bullet in the search..