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Missing and spluttering at 4800-5500 1993 Lemans V1000

Supaflee

Cruisin' Guzzisti
Joined
Apr 17, 2012
Messages
201
Location
Tauranga, New Zealand
Today I went for a ride on my 1993 Ultima Edizione Lemans . Wow what a buzz . After about 100 Ks , when I'd settled into it a bit and gave her a handful in 3rd , 4th , and 5th , I noticed surging and missing in each gear , when at wide open throttle she reached about 4800 through to 5500 Rpm and a very distinct lack of power at the same time as she struggled through that rev range. Wide open throttle remember , main jet territory I think. Yet once it got above 5500 Rpm she'd pull cleanly through to over 6000.
Interestingly , the more often I did it , the less appearant the fault was . The rev range narrowed somewhat , but the spluttering and missing and lack of power was very evident.
Before I start taking things to bits I figured I'd just ask the question of you all . I havnt started searching yet . Please help .
Supaflee
 
With these big 40mm Del O'rtos the slower you move your hand on the throttle, the better the response. If you just go to full open, you get a bunch of air, low manifold vacuum, and no fuel. Try more gradual opening of the throttle. Works for me on my Mk V. If you still get the issue, check the accelerator pumps and maybe for worn cam chain which will impact ignition and valve timing.
 
Ah ha , I think you may have a good point there John.
At the time the missing was most noticeable , I'd hauled the throttle wide open in one single movement , thinking I'll just wind her up a bit from 4000 with wide open throttle all the way . Never for one moment recognising what may be happening in the inlet manifold , low vacuum , that makes sense.

Cam chain ,,,,,, mmmmmm, at 55000ks. I'll try to determine the manifold pressure causing low fuel theory first .

Next time I go riding I'll see what happens and report again at that time .
Is it ok to run this engine at high revs , say to 7000 occasionally ?

Here's something else I noticed when she was pulling up into the 5000 rev range , there is a beautiful , "Guzzi Only ", sweet turbine screem sound coming from the induction snorkel under the tank . Now that's real cool. Do they all do that ?

Regards Supaflee
 
Supaflee said:
Next time I go riding I'll see what happens and report again at that time .
Is it ok to run this engine at high revs , say to 7000 occasionally ?

Yes, the redline is conservative on these bikes. Just realize the high RPM may increase ring wear with the higher piston speed. Still it is better than lugging the engine.

Supaflee said:
Here's something else I noticed when she was pulling up into the 5000 rev range , there is a beautiful , "Guzzi Only ", sweet turbine screem sound coming from the induction snorkel under the tank . Now that's real cool. Do they all do that ?

Regards Supaflee

Yep, the high air velocity through the smallish snorkel. It doesn't seem to hinder performance much.
 
JZ , Ive just found out that the 98 Octane fuel I'd put in the tank contained 10% Ethanol.
Here's a little background , When I bought the bike recently it had very little fuel in it and it pinked like hell, even under slight excelleration . I filled the tank , 20litres , with BP 98 Octane . No more pinking , but I also never gave it a real handful of throttle either . ( this was at the time I asked what Octane I should be using )
Lastly , I filled the tank 18.8 litres of Gull 98 Octane , which contains 10% Ethanol , and I have the huge dead spot in the excelleration as I described earlier in the post.
Soon , I'll refill the tank with unadulterated 98 Octane and see what the differences are , watch this space .
Regards Supaflee
 
Ethanol has nothing to do with it. 10% 93 octane is the best I can get and I don't have your issue with my Mk V. Just consider the 10% to be using dry gas in your fuel all the time.
 
Hhhhmmmmmm, ok . It looks to me as though another test run is required . Goody !!
I'll just wait for the right moment , and until I know there's a conference or a meeting of some sort to otherwise occupy the patrolling police , then , zooooooooooooom.
I'll report again later .
Thanks for the help JZ
Regards Supaflee
 
The fuel might not be the sole cause of your flat spot but it could well be a contributing factor. My Ultima Edizione was very sensitive to fuel. Not only did the warning on the tank say to use high octane but I found some brands of fuel better than others and it varied thru' the seasons as here in the UK the fuel companies tweak their recipes from month to month and it can vary depending on which refinery it has come from!
 
Thanks for that Will.
So , not altogether an unfamiliar problem by the sounds of your feedback.
With this info in hand , I'm going for some trial runs later today , using the 98 Octane BP fuel.
Im wondering now if , maybe its a combination of too much throttle along with an unsuitable fuel as well. The test rides will tell me one way or the other.
Thanks for your help .
Regards Supaflee
 
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