Carb tuning for a 150RS - MVAgusta.net
 
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post #1 of 7 (permalink) Old 02-20-2017, 02:29 PM Thread Starter
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Carb tuning for a 150RS

Hello everyone again. After a cold winter here in south of Germany, and some hours in the garage with my latest bike. I was able to fix some of the issues of this 150RS. So the other day, me and my girlfriend we tried to start the bike up after 20 years sitting in a living room. We didn't expect to start it up actually, but for our surprise, the engine gave spark and it fired for two or three cycles.

GREAT! We screamed. But the engine went off. This went on for the whole afternoon. (Even with push start). The engine fires well, but just can't keep the spark alive.

My guess is the carb and the tuning is not the correct one. It comes with a DELLORTO MB18b. The mixture screw is 2turns from tight, and the idle gap is around 1.5mm , dont remember the needle setting now, but i can check that.

What do you guys think?

Best regards
Dong

Last edited by DongXu; 02-21-2017 at 10:29 AM.
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post #2 of 7 (permalink) Old 02-21-2017, 10:32 AM Thread Starter
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Never mind, Solved after cleaning the carb again , and made it 2,25mm gap for the idle ( 18mm x 1/8 (according to the dell orto manual book) ), cleaned the mixture screw holes with a very thin wire . The bike runs well at idle now.

How ever if you have any setting for this Carb, welcome to hear that.
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post #3 of 7 (permalink) Old 02-22-2017, 02:43 AM
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Hi Dong Xu,

Dell'orto original setting data for the 150 MV are :

Carb : MA18B
needle : D12 second notch
atomiser : 260B
throttle cut : 60
main jet : 72
idle jet : 40
float weight : 6.5 gr

All the best
Dominique

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post #4 of 7 (permalink) Old 02-23-2017, 08:09 AM Thread Starter
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Quote:
Originally Posted by GTW36 View Post
Hi Dong Xu,

Dell'orto original setting data for the 150 MV are :

Carb : MA18B
needle : D12 second notch
atomiser : 260B
throttle cut : 60
main jet : 72
idle jet : 40
float weight : 6.5 gr

All the best
Dominique

Hey Dominique,Thanks a lot for this info. I have the needle at the first notch right now. I will try the second notch after my lunch hehe. The rest of the components are corrent and clean. I guess I won´t need a replacement.

So far I have the mixture screw at 2 turns from tight. What do you think?
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post #5 of 7 (permalink) Old 02-23-2017, 10:21 AM
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Hi,

As reference setting, the mixture screw should be 1.5 turn unscrewed, but setting range from 0.5 to 2 turns is normal.
First notch from the top of the needle is a leaner setting than original.
So the 2 turns on the mixture screw (richer) may be needed to balance the needle setting
With the needle at the second notch, may be the mixture screw will be fine with around 1.5 turn.

All the best
Dominique

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Last edited by GTW36; 02-23-2017 at 10:26 AM.
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post #6 of 7 (permalink) Old 03-07-2017, 02:06 PM Thread Starter
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Quote:
Originally Posted by GTW36 View Post
Hi,

As reference setting, the mixture screw should be 1.5 turn unscrewed, but setting range from 0.5 to 2 turns is normal.
First notch from the top of the needle is a leaner setting than original.
So the 2 turns on the mixture screw (richer) may be needed to balance the needle setting
With the needle at the second notch, may be the mixture screw will be fine with around 1.5 turn.

All the best
Dominique

Great Dominique, you are the best.
I have now the needle at the second notch and the mixture screw at 1,25 turn unscrewed. The engine feels nice, and health at idle and middle revs. However I can hear a "hammering" noise when I rev up (to i guess + 3000rpm). Is this normal? The carb setting now feels good and at the top gear, the bike pulls really good.

Best,
Dong
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post #7 of 7 (permalink) Old 03-13-2017, 09:00 PM
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Quote:
Originally Posted by DongXu View Post
Great Dominique, you are the best.
I have now the needle at the second notch and the mixture screw at 1,25 turn unscrewed. The engine feels nice, and health at idle and middle revs. However I can hear a "hammering" noise when I rev up (to i guess + 3000rpm). Is this normal? The carb setting now feels good and at the top gear, the bike pulls really good.

Best,
Dong
Hi Dong,

"Hammering" could be several things including pre-ignition as a result of the the mixture being too lean or even the fuel being too low octane. Be very careful of this as the bike will make more power in a lean state but the engine will not be able to cope with it.

It might also mean the valve clearances might need adjusting.

It it was my bike - id pull the spark plug out and look it - if the colour is very light it is too lean, if very dark too rich, you want almost a a creme coffee colour. After that, I pull I'd check the valve clearances. If those things are in order and it still does it then you need to figure out how far you want to go because the next step is to tear down the motor and have a look from crankshaft up, I wouldn't suggest that at this stage unless it is particularity bad or getting worse.

These old engines are a little noisy to start with (oil filtration was never the greatest) so you need to factor that in also.

Cheers
Rob


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