2000 Duc Monster 750 - Intermittent Problem - Help!

[Javamoose]

So, I had this problem twice now in about 600 miles.

Problem:

Bike will start to hesitate when giving it throttle. Runs, but if I give it any gas it will hesitate and/or stall.

First time it happened:

After about 80 miles of non-stop riding, hit a section with a lot of traffic and it was first-gear go ten feet then stop for about 20 minutes. After getting past the traffic, I was in third gear running fine, went to accelerate and nothing. Twisted the throttle and it just bogs down, hesitates, then goes. Rinse and repeat. Pulled off the road, in neutral, gave it gas and it hesitates, pops, but doesn't really rev. Pulled the seat, lifted the tank, strong fuel smell. Drained the bowls, clear gas, no water or crud. Let it sit for 15 minutes, thumbed the starter and it fired right up and ran fine for another 50 miles until I got home for the night.

Ran like a champ all the following week and through a 130 miles ride the following weekend.

Second time it happened:

Short ride, 5 miles through medium traffic. 15 minutes spent in first, stop and go, through a parking garage at the mall. Visit friend in store. Come back out after 30 minutes. Bike fires up, ride through parking garage, just as I get out to the street it starts with the throttle but no rev/gas thing. Little bit of throttle and it stalls. Hard to start, flip the choke open and it fires up but runs rough. Still no throttle response. Close choke and it dies. Pull bike onto the sidewalk, remove seat and lift tank. Strong fuel smell, but no leaks found. Let bike sit for 15 minutes and she fires right back up and runs strong all the way home.

One of the guys in the group I ride with, knows bikes, older guy with a lot of experience, thinks the bike may have sat for a few years before I bought it. Guy I bought it from said he had been riding it for a year right up until I bought it. The inside of the tank has some sort of white coating on it, which is peeling and missing in most sports with some oxidation on the exposed areas.

Oh, you can smell gas in both exhausts, but one pipe smells stronger than the other.

[ducpainter]

It sounds like the tank was coated with Kreeme and it has failed.

Those flakes could be blocking the fuel outlet of the tank and causing the hesitation/stalling.

The rich smell is probably a different issue. How many miles on the bike?

[Javamoose]

I bought it with 16,000 miles on it...now has about 17k.

[ducpainter]

I bought it with 16,000 miles on it...now has about 17k.

If the bike runs kinda rich at cruise the needle jets/emulsion tubes are probably worn.

Are the plugs sooty?

[Javamoose]

If the bike runs kinda rich at cruise the needle jets/emulsion tubes are probably worn.

Are the plugs sooty?

I haven't checked the plugs yet, but will do today. 

It always seems to idle high to me, after I've been riding for a bit, when I stop at a light it sounds like it's idling high, if I let the clutch out until it grabs a little bit, then pull the clutch back in the idle will drop down to a slow idle.  However, sometimes if it's a long light the idle creeps back up over the course of a minute or two.

[ducpainter]

That can be caused by a couple of things.

One is the carbs being out of synch. The other would be too high of a warm idle. The way the ignition advance works on the carbed bikes is rpm sensitive so if the warm idle is over 1200 rpm the ignition will advance and the idle will 'hang'.

It sounds to me like your bike could use a good tune up.

Where are you located?

[Javamoose]

It sounds to me like your bike could use a good tune up.

Where are you located?

I agree, I recently bought the bike...overall it's in good shape, but I don't think ANY of the maintenance was done (other than oil changes).  I'm planning on doing the valve clearance and the cam belts.

I'm in Honolulu.

[ducpainter]

Maybe you could introduce yourself over in DesmoTropic and one of the locals can point you in the right direction for a tech.

If you have the tools the carbed bikes are pretty easy to work on and you can get all the advice you need here.

Don't wait too long for belts. I'm not a doomsayer, but I have seen the consequences of a broken belt. It isn't always a disaster, but it's not worth the chance IMO.

[Javamoose]

Maybe you could introduce yourself over in DesmoTropic and one of the locals can point you in the right direction for a tech.

If you have the tools the carbed bikes are pretty easy to work on and you can get all the advice you need here.

Don't wait too long for belts. I'm not a doomsayer, but I have seen the consequences of a broken belt. It isn't always a disaster, but it's not worth the chance IMO.

Do you have to drop the engine to do the belts?  'Cause I can't see how you would get at them and get the covers off with the frame in the way...

[Duck-Stew]

Remove the covers, loosen the tensioner and the belts come right off without removing the engine from the frame.

The horizontal cylinder will line right up and go right on, but because the vertical cam is trying to lift a valve at that point, the belt installation is a might trickier.

+1 to the Kreeme failing and blocking the fuel outlet from the tank.

[ducpainter]

What he said...

[Javamoose]

Ah, ok...makes sense.

With regard to the tank issue, how does one go about cleaning that crap out of a tank?  The bike has a custom paint job that I kinda like, so I wanna try to avoid ruining the paint on the tank or eBay'ing a new tank.

[Duck-Stew]

Ah, ok...makes sense.

With regard to the tank issue, how does one go about cleaning that crap out of a tank?  The bike has a custom paint job that I kinda like, so I wanna try to avoid ruining the paint on the tank or eBay'ing a new tank.

Try talking to a moto shop local to you (or a painter that does moto-tanks) and see what they say.  You may have options and you may not...  Depends on what chemicals they allow in Hawaii.

[printman]

Oh, you can smell gas in both exhausts, but one pipe smells stronger than the other.

Should have a crossover pipe on the bottom so they shouldn't really be different?

Fix the peeling problem, replace the fuel filter


Idle can be sync issues, I have used a cheap vacuum gauge when I had stock carbs. Idle to me is touchy, should be around 1100 a little over and it will hang up to around 2000, that is from the advance in the ignition system. adjust idle screw to fix.

[ducpainter]

Ah, ok...makes sense.

With regard to the tank issue, how does one go about cleaning that crap out of a tank?  The bike has a custom paint job that I kinda like, so I wanna try to avoid ruining the paint on the tank or eBay'ing a new tank.

The Kreeme will dissolve with MEK. I've removed it before and it takes about a gallon used in three steps to completely remove it.

It will hurt the paint if you're sloppy, but if you're careful you won't hurt the paint job.

I'm wondering if the tank was leaking from the hinge and someone Kreemed it. If you look underneath around the hinge does it look like it's been welded?