1997 M750 Won't start, not sure what to do at this point. - Ducati Monster Forums: Ducati Monster Motorcycle Forum
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post #1 of 12 (permalink) Old 02-20-2017, 04:18 PM Thread Starter
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1997 M750 Won't start, not sure what to do at this point.

Hello all,

I have a 1997 monster 750 that I've had for about 2 months. It has ~40,000 miles on it, and worked fine the first few weeks. One day it died at a stoplight and would only run at idle and die under throttle. I suspected this to be a clogged jet problem, so I took apart the carbs and cleaned them. I put it back together and it still dies.

I had to leave it sitting for a month due to being out of town, and when I came back it only turns over but doesn't start. The battery is brand new and charged, and works fine. I tested the fuel pump by removing the hose from the carb and cranking it, and it pumps gas out. When I pulled the carb float bowls off there was fuel in the bowls so I know it is getting fuel. I also noticed there was a white gel substance in the bowls, which I suspect to be the ethanol to be going bad in the gas.

I also replaced the spark plugs, and the plugs looked fine. I tried cleaning the carbs again and i was able to get it started and was able to ride it for about 5 minutes, but it would die under heavy throttle and then up a slight hill it bogged and then died completely. It now doesn't start again. There is a little bit of 2 month old fuel in it (~1 gallon) so I went and added a gallon and a half of new 91 octane fuel and some Chevron Techron fuel treatment. It still won't start. I'm not sure what to do at this point . Anyone have any ideas?
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post #2 of 12 (permalink) Old 03-03-2017, 02:53 PM Thread Starter
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Anyone? I still cant figure it out...
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post #3 of 12 (permalink) Old 03-04-2017, 06:55 PM
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I would suspect your on the right track...degunking the carbs...dying under load sounds like a vacuum leak...or an airflow problem...
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post #4 of 12 (permalink) Old 03-05-2017, 10:07 AM
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Are you certain the vacuum petcock is opening correctly? That the vacuum tubes to it are not cracked or missing?

Is the vacuum fuel pump connected and working?

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post #5 of 12 (permalink) Old 03-05-2017, 11:48 PM Thread Starter
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I'm not sure how to tell if the vacuum petcock isn't working, it didnt look like any of the hoses were cracked on it though. Is it possible that the fuel filter is causing these issues?
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post #6 of 12 (permalink) Old 03-06-2017, 10:24 AM
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Another possibility is the fuel pump. If your inspections and testing all leaves you at a loss, check the pump.
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post #7 of 12 (permalink) Old 04-19-2017, 01:22 PM
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I had some similar issues with my 2k M750 last year that were resolved by a full carb rebuild.

Not sure that helps a lot but I was having a very similar not start/bog down/die out issue.

Keep the dirty side down.
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post #8 of 12 (permalink) Old 04-19-2017, 01:58 PM Thread Starter
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Quote:
Originally Posted by hinesmatt View Post
I had some similar issues with my 2k M750 last year that were resolved by a full carb rebuild.

Not sure that helps a lot but I was having a very similar not start/bog down/die out issue.
Did you fully rebuild the carb? I took it apart and put New gaskets and a new float valve, but I'm not sure if that's considered a full rebuild or not. I have good compression, ~135psi per cylinder so I'm sure it is something to do with the carb.
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post #9 of 12 (permalink) Old 04-19-2017, 02:03 PM
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I'm non-mechanical. Handed over to dealership mechanic who rebuilt [part of the expense was full carb "rebuild kit" so I'd assume they used all the parts involved]. Again, I just had a similar issue and this seemed to resolve it [thus far, about 200 miles in after service].

Keep the dirty side down.
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post #10 of 12 (permalink) Old 04-19-2017, 02:12 PM Thread Starter
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Originally Posted by hinesmatt View Post
I'm non-mechanical. Handed over to dealership mechanic who rebuilt [part of the expense was full carb "rebuild kit" so I'd assume they used all the parts involved]. Again, I just had a similar issue and this seemed to resolve it [thus far, about 200 miles in after service].
Hmm ok, I'll probably do more research, the gaskets and and float valve were sold as a "full rebuild kit". I definitely appreciate the feedback from you though, it helps to narrow it down since you had a similar problem. Thanks!
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