[brodg]

So went out for a ride the other day on my bike and it was going great, then once I had been on it for about 20 minutes the rpms started jumping up and down. I kept on driving thinking that it might've just been something in the gas that it needed to burn off, but unfortunately it started doing it again a few minutes later. The clutch on the bike is definitely on its way out (when I changed the oil there was fragments in the oil of clutch) so i'm not sure if this is a issue with the clutch. But what the bike does is you can shift it, but it has a serious loss of power. Not just this, but the tachometer shows nothing. And when the bike does perk back up, the tach will show the proper RPM's. I tried searching for videos of this but I haven't had any luck. I'm gonna call the local bike shop and see if they have any idea as well, but figured I would ask on here to see if anyone has had or heard of this issue before. I plan on changing the cam belts and clutch this weekend. Any help or advice is greatly appreciated!

Bill

 

[dspear99ca]

If you put your bike info in your signature, then we know what year/model of Monster you have. There are a lot of iterations out there.

Tough to say what's going on without knowing the year... old Monsters have tach cables, broken cables tend to work sporadically but it sounds like your issues are bigger than that.

I'd start by checking battery voltage and grounds, ECU ground. Check electrical connections to your igniters/coils. Check for corrosion around fuses, etc.

Is the RPM display (assuming you have ECU & LCD dash) just going to zero, or is the display cutting out entirely?

 

[brodg]

Okay just did it!

 

[dspear99ca]

Huh. Well, it's carbeureted (no ECU) with a mechanical speedo (cable with spinning core) but electronic tach. The tach is driven by the igniter output of the vertical cylinder. That's where I'd start to look. Loss of power corresponding with tach dropping off sounds like loss of output from the V igniter. Check all wiring, the V and H igniters each have their own pickup. Check power and ground connections and wiring for each ignition module (igniter) as well. If the wiring checks out and there's no obvious connection issues, swap the V and H igniters, they're identical. If the power issue persists but the tach now works perfectly, suspect the ignition module which is now on the H cylinder. If the problem stays the same, i.e. tach still acts funky, then it's either the pickup itself, pickup wiring, or power/ground wiring to the V igniter.

 

[casor]

I presume when you have the rev fluctuation the bike is being run under a load as opposed to idling or revving in neutral. Since you mention that the clutch appears to be toast, don't overlook the obvious. Under load, the clutch may be slipping. A broken tach cable or elec issue would cause a rev fluctuation (or no reading at all) regardless if the bike was under load or not.