2000 M750 w/ black spark plugs. Got questions...

[rnicholson]

Hi,

upfront disclaimer -- I'm new to motorcycles, and I previously have never owned any vehicles (cars or otherwise) with a carburetor -- so new to carbs as well... so go easy on me  

I have a 2000 Monster 750 (carb) that I bought about 140 miles/~1 1/2 month ago (bike has 15K total miles). Recently, I was surprised a bit at the gas mileage. It seemed low; ~35mpg. but honestly I didn't make rigid measurements on gas in/miles out --  only dumped about a gallon or so in, and went for a ride (~35 miles) and the fuel light came on about ~15 miles into the ride. Tank was basically empty, before filling up (I'd drained the tank in a failed attempt to swap tanks the day before, but that's another story...  ).

So, I decided to just pull the plugs on it and check them out. They are really black, not nice coffee brown. So, strong evidence its running rich. I've already ordered new plugs (NGK DCPR8E - or are there other recommended ones?).

After poking around on the boards here (and googling), I'm guessing I also may need new needle jets? FP CRZ-EMU-100120K a good choice?

Also, once I replace the needle jets, do I need to resync and/or adjust the carbs? Like I said, carb maintenance/tuning is new to me... so a bit hesitant to make unnecessary changes , not to mention get in over my head (I've done work on cars before -- oil changes, exhaust/bolts-ons, suspension,etc -- but no master mechanic) and potentially have an nonfunctional bike during prime riding season With that said, are there other tutorials on doing jetkits/carb adjusting?  I've seen http://www.ducatisuite.com/jetkit.html -- which is great, but curious if there were others I should read (I also got a Haynes manual with the bike when I bought it).

another related question -- When I bought the bike, it came with a K&N drop-in filter. Unclear, cause I didn't really know to ask at the time, if it was rejetted or other adjustments made. The bike idles well. Typically needs to start with the choke, regardless of temp. Although, honestly I don't have a lot to compare it to. Sounds fine when riding (although not the best ride at sub 20mph). No backfiring or hard popping that I've noticed. So, with just a K&N drop in do I need to add a jet kit? I see other posts about having an open/cut air box or using cone filters needing a jet kit. If I'm going to go through the effort of changing out the needle jets, so should I get a jet kit as well and do it all at once?

Thanks in advance for any help or other advice...

[memper]

1) what pipes do you have?
2) are the plugs dry and dark or wet and dark?
3) what makes you think you need new needle jets? Only real way to tell is by removing and inspecting them.
4) while taking them out, remove the pilot and main jets too. Inspect for wear and note the sizes. Might as well measure the float height while you're in there too.
5) yes you will likely need to re sync and adjust the carbs after removing them. But it's no big deal and its good for you like broccoli.
Hardest part is getting the damn throttle cables off and on again.
6) don't get a jet kit until you have done #4.
7) most importantly, you are on the best darn Duc forum there is. Help if necessary is always here. Even for turds like me.

[koko64]

All good questions to consider.

At 15000 miles its likely that your needle jets are worn. This will let through too much fuel and is a common cause of fouled plugs on bikes with these carbs. As is mentioned often, replace them wigh Factory Pro needle jets from one of our sponsors.

A jet kit with an open airbox with K&N or BMC filter and free flowing slip on pipes is a good mod many have done.
I think you should replace the needle jets and see what jets are in there before buying a jet kit, as they are a common mod. The bike may already have a jet kit installed and possibly set up too rich.

The oem needle jets are a brass color and the FP ones are shiny nickle or stainless looking. You will see the tops of the needle jets where the needles go into the bottom of the carb throat.

Let us know what you find.

[ducpainter]

You don't need to remove the carbs to change needle jets.

Some find it easier to do so because it's tight in there.

I do it with the carbs installed.

[MotoPsycho]

Inspect the diaphragm boots too when they come out to get to the needle jets. I had one with cracks on it.

[rnicholson]

All -- Thanks for all the good replies and info...

1) what pipes do you have?
2) are the plugs dry and dark or wet and dark?
3) what makes you think you need new needle jets? Only real way to tell is by removing and inspecting them.
4) while taking them out, remove the pilot and main jets too. Inspect for wear and note the sizes. Might as well measure the float height while you're in there too.
5) yes you will likely need to re sync and adjust the carbs after removing them. But it's no big deal and its good for you like broccoli.
Hardest part is getting the damn throttle cables off and on again.
6) don't get a jet kit until you have done #4.
7) most importantly, you are on the best darn Duc forum there is. Help if necessary is always here. Even for turds like me.

1) Stock pipes.
2) dry - black.
3,4) Yeap - good points. Its probably worth fully inspecting the carbs before replacing parts.
5) OK cool -- hey, I like broccoli
6) OK cool. Saves me some $$$.
7) Agree! -- this place is chock full of good info...

[memper]

Inspect the diaphragm boots too when they come out to get to the needle jets. I had one with cracks on it.

Yes. Hold the slide part and hold the diaphragm in front of a light and hope you dont see any pinholes of light showing up.

[beethoven]

I agree with all above and have replaced needle jets on 97  900. One other thing which the earlier carb engines don't like is high octane fuel. My plugs kept fouling until I changed back to regular grade.

[rnicholson]

I agree with all above and have replaced needle jets on 97  900. One other thing which the earlier carb engines don't like is high octane fuel. My plugs kept fouling until I changed back to regular grade.

Hmm. I have been using 93. Previous owner said he did too. Manual said to use 95-98 RON -- which I thought here in the US translated to either "mid-grade" (89) or "premium" (93).

[Howie]

Hmm. I have been using 93. Previous owner said he did too. Manual said to use 95-98 RON -- which I thought here in the US translated to either "mid-grade" (89) or "premium" (93).

Numerically, but not in terms of performance.  Our number (AKI) is RON + MON devided by 2, giving a numerical average.  the RON test sequence is different than the MON test sequence.  Your 750 is Ducati's lowest compression engine and 87 is probably more than it needs.

[Radracer6]

This is so similar to the 2001 M600 I got a month or so ago. I am new as well to carbed bikes but I am learning.  I also need to start my using the choke regardless of temp outside like yours. Also I've poured 93 gas in it since I got it like you so I'll try regular 87 on next tank. My bike has stock airbox but looks like last owner has a K&N square filter in there.

My bike has 24k miles. When i pulled the plugs they were dry black like yours. It actually turned off on me on the highway once so I replaced the fuel filter and fuel hose from the tank and the plugs. I've cleaned the carbs using gas and a compressed air can and used instructions I've found online, I also re-jetted it using factorypro's kit and adjusted the mixture scews and floats to the specs they suggested.

I've had trouble starting it recently and after I got it going it sounded like it was running on one cylinder and struggling in first so I will be pulling the plugs again to see if I fouled one. I'm wondering if the idle mixture screws are too far out? factorypro recommends 3.5 out after re-jetting. Either way I'm curious to what you find.

[Howie]

All good questions to consider.

At 15000 miles its likely that your needle jets are worn. This will let through too much fuel and is a common cause of fouled plugs on bikes with these carbs. As is mentioned often, replace them wigh Factory Pro needle jets from one of our sponsors.

A jet kit with an open airbox with K&N or BMC filter and free flowing slip on pipes is a good mod many have done.
I think you should replace the needle jets and see what jets are in there before buying a jet kit, as they are a common mod. The bike may already have a jet kit installed and possibly set up too rich.

The oem needle jets are a brass color and the FP ones are shiny nickle or stainless looking. You will see the tops of the needle jets where the needles go into the bottom of the carb throat.

Let us know what you find.

[Radracer6]

yep Howie, saw that part I already have needle jets from factorypro on the way.

[J-Cee]

So what was the verdict? I'm in the middle of carb tuning right now. Runs great everywhere except idle.

[rnicholson]

So what was the verdict? I'm in the middle of carb tuning right now. Runs great everywhere except idle.

Wow. Crazy timing, I was just about to reply to this...

First off thanks a ton for all the advice given here. It was a big help!

Initially, I changed the plugs, and checked the mixture screws -- and they were out of whack -- front was 4.75 turns; top cylinder was 4. Put them to 3. Did about 170 miles like that, and bike seemed great all around, and gas mileage seemed to be much better -- ~40mpg (2 gallons in - ~80 miles from first time low gas light was solid on to fill-up to next time gas light was solid on). Also, been running 87 now after recommendations here and research of my own and now concur -- it runs better than with 93 octane.

I just replaced the needle jets (new FP ones) literally like 2 hours ago -- hard to tell with the naked eye if the old ones were worn, but they were brass ones, so assume they were original stock. I spent most of yesterday getting it all apart (first time so was going slow) and getting some of it back together (striped one of the float bowl screws -- so had to make a trip for some M5s). Got it all back together this morning. As an aside -- What a freaking pain it is to get the damn throttle cable back on! I wasted like a hour fumbling to get it set -- memper was 100% dead on about that. Checked float heights and they were at 14mm each; so seemed right based on searches (why doesn't Ducati or Haynes publish these?). Diaphragms looked good, no holes that I could find. I was a bit nervous as it took a bit to start once it was all back together (again first timer), but just assumed it was cause the fuel lines and float bowls where empty... but when it fired up I was all smiles (love it when you can get things back together and it still fires up haha  ).

So, far so good...