mugello 200 high compresion

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tavspeed
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Fri May 18, 2018 8:22 pm

hi all,mate has bought a chopper with a newly built mugello 200 in it,straight from the off it had really high compression,and sure enough the kickstart packed in,have replaced kickstart piston and ground the shaft back as it was not returning,as was catching the clutch,but is really hard to kick over due to the compression.
is this normal on a mugello as have read somewhere the heads where of dubious size quality,cheers all

stew
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Fri May 18, 2018 9:50 pm

Which version as I had compression issues on a v3 , possibly why the v4 came about
Loud pipes save lives!!

Adam_Winstone
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Mon May 21, 2018 7:04 pm

All depends on how it has been set up and what other components it has been mated with.

Yes, the Mugellos can be high compression, noting that the specification has changed over the production and development period, but you need to remember that they were designed to be most suitable with Tino's range of products. Considering that the Varitronic has an ignition curve that starts low at tickover, then advances slightly, then retards again as the revs increase. This ignition curve is especially designed to ease kick-starting, accelerates well from low RPM, runs strongly through the mid-range, then stays cool... even with high comp. If the motor is running static timing or one of the bolt-on modules that doesn't have the low start and initial advance then starting will require quite a kick.

High comp... yes, very likely (I found mine to be pretty high comp) but it makes sense if you look at the components that it was really designed to run with, especially Varitronic. It can easily be configured to work and run well with other components but it may benefit from careful consideration of setup, rather than just bolted on (please note that I'm talking in general and not implying that the builder in this case didn't give due consideration).

Measuring the head's volume (whichever method you might choose) is the only way to really know what you're dealing with.

Good luck getting it sorted.

Adam

tavspeed
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Thu May 24, 2018 10:55 pm

hi chaps thanks for the input,kickstart fixed and now running again,but it is on a dellorto 30 phbh and franspeed race,jets are 125 main x7 needle av268 atomiser and 55 pilot,2nd clip from top on needle,the motor seems to be running lean,he had to put choke on to get it to ride back home from a test ride,no obvious air leaks anywhere,any thoughts

tony172
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Mon May 28, 2018 12:09 pm

My best mates using the mugello 198 and it's got very high compression. Snapped a kickstart gear last summer too. You're not alone

Adam_Winstone
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Mon May 28, 2018 12:36 pm

In which case you better make sure that you're running low ignition advance, if static, otherwise you may run into issue. The problems really start when you use high comp heads on barrels that do not have considerably increased exhaust port durations, which results in high corrected comp ratio.

High comp heads are not an issue, providing the porting and ignition profile suit accordingly. However, the combination of high comp head, low exhaust port duration and/or over advanced ignition timing is a recipe for seizure or a hole in the piston. This is a good example of why a motor should be considered as a whole, rather than just an assembly of 'off the shelf' components.

PS - On today's hot burning fuels (ethanol and detergents) I don't particularly like high compression or over advanced ignition timing, both factors that can cause a motor to run too hot.

The only way to address this is to know what you're dealing with (measure head volume and assess port specification) and to talk to someone who can give some decent advice. IMO you can't beat talking to Cambridge Lambretta or one of the other respected Tino kit outlets.

I hope that you get this resolved to your satisfaction.

Adam

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