UK Monster Owners Club Forum » .: Technical :. » Engines, Clutch, Gears » another dead M750

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Old 11-09-2021, 04:15 PM   #1
jerry
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another dead M750

So the rebuilt one is still dead because it cant run cleanly its something to do with ignition but no one has a clue anymore ,its sitting in a Marinos work shop but he is scratching his head after messing with it for a week and putting new pickups on , but now my other M750 has a problem Fuel starvation ,, its not the carbs , bike starts runs for a few minutes but does not rev , and then dies,, lift up fuel tank and it will start but run for a couple of minutes then same issue ,, vents are all clear ,, fuel filter new and fuel pump was rebuilt with new parts last year ,,,?? could be vacuum tap???
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Old 11-09-2021, 06:06 PM   #2
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OK seems it may be the fuel filter which was replaced in January according to my records when the original actually snapped on of its spigots ,, the new one is completely gunged up with some yellowish slimey crud (gasohol) ???????? after isolating it from fuel circuit seems the bike may be OK again ,,,I will get a new filter on monday will test ride it locally tommorow to be sure ,, worrying though as I only fill up with pure petrol or E5 and always fill up now with super/premium E5 fuel ??????
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Old 12-09-2021, 09:10 AM   #3
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opened the carbs up today some of the yellow slimey crud was in the float bowls ,, the bike is running better again must have got some contamainated fuel with E10 in it ????,, only 1 week into September and already petrol supply issues ,, I only by super premium so how did this crap get into my tank ???
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Old 12-09-2021, 11:12 AM   #4
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Probably ethanol based jerry, what's in their seperates out surprisingly quickly and the water sinks to the bottom of the tank. Then you get the rusting and frequently some anaerobic growth.
How did it get in there, well odd that. I do remember once I got diesel as a top up in a bikes fuel tank, I really didn't think that I'd got the wrong pump. Then I heard that a couple of cars had the same problem, a delivery had dumped diesel into the premium tank. So really you don't know whats coming out of the spout at the garage, we all just assume it's what's on the label.
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Old 13-09-2021, 09:32 AM   #5
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my friend John has a Yamaha XJR 1200 carb model he called me yesterday ,, same problem but he lives in Hastings and has not filled up at same stations I use ,Shell and BP around west sussex , he says bike was fine but he rode out 2 times last week filled up with super premium E5 from Texaco both times and the bike carbs and filter are blocked with slimey yellow snot same as my M750 ???

however his brother has an old mint condition Suzuki GT380 3 pot stroker and it runs fine on E10?????
WTF???!!!!!!
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Old 13-09-2021, 12:10 PM   #6
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Quote:
Originally Posted by Nickj View Post
Probably ethanol based jerry, what's in their seperates out surprisingly quickly and the water sinks to the bottom of the tank. Then you get the rusting and frequently some anaerobic growth.
How did it get in there, well odd that.
While the ethanol will separate out when the fuel is exposed to moisture, in normal circumstances this is not going to happen spontaneously via absorption from the atmosphere - especially in this country at this time of year. If there has been separation, it must be the result of contamination, either at the petrol station or in the bike's tank.

Typically, E10 will need to absorb 0.5% water before phase separation takes place. So, for a tank with 15 litres of E10, you would need 75ml of water to start the process. The resulting water/ethanol layer will contain approximately 3-4 parts ethanol to each part water. So the 75ml of water would produce a water/ethanol layer of, say, 375ml. (To draw out the maximum ethanol of 1.5 litres, you'd need at least 375ml of water.)

So you could have a situation where there's been a small amount of water sitting at the bottom of the tank for months, undetected because it's below the fuel pump's intake. However, if you then fill up with an ethanol blend, that small amount of water would cause a rapid phase separation, (within 30 minutes), and suddenly that previously unnoticed contamination has increased five-fold, its level has risen and is now being drawn into the fuel pump and causing fuelling problems.

So this is basically a very long-winded post to say to make sure there's absolutely no water in your tank!
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Old 13-09-2021, 07:21 PM   #7
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Just had a weekend on the IOW, and got petrol twice and both times only E10 available. I was on my modern trumpet so that's fine.
I was with my dad and the Norton owners club riding bikes from the 50's and 60's. Not many of them were co cerned by the E10. Petrol was crap back then and if it ends up choking up the carbs, just clean and carry on.
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