Monty race project

Fitz

Fitz

Senior member
Location
Cheshire UK
Does anyone have any knowledge of carb jetting on high performance 500 engines

I have a very high compression motor, BB ignition, big bore exhaust system and standard Delorto PHF carbs, S1 cams

The manual shows main jet size 115 but mine already have 140 main jets

I am using 98 octane standard fuel

Cheers gents
 
No idea Fitz, but I would certainly let a dyno help with the choice, via AFR measurements.

Getting it wrong on an 'very HC' motor could quickly go from inconvienient to expensive!

Good luck.
 
Although it is not really a high performance engine my Monty uses 140s as standard with S1 cams, think it's the Alpino that uses 115s.

I used Shell  V- Power plus Millers CVL as a preferred mix.
 
Hi Fitz,
When I was last using Dellorto's I had 155 main jets in.

Best advice I can give is put the bike on a dyno and set the carbs up that way.

The bike will thankyou for doing it.
Make sure you have a selection of main jets when you go.

Andy
 
Just for interests sake, wifeys' 500 currently runs 95 mains, set on a dyno using CO analyser many years ago (no affordable Lambda sensors around back then).  Was getting used to achieving some wierd cam/jet/exhaust combos, but this really surprised me.  Stock carbs and cams with LOTS of compression, big valves and a more-or-less road-legal exhaust.  :D  Goes like the clappers!

piet
 
Had a long discussion with Ducati mechanic on Dellortos settings with the modern fuel. He has taken to changing the AB265 to a AB264 to lean through the whole throttle range. His reason being the modern fuel has a lower Sg (thinner) and flows differently. He said he is back to getting Gray plug readings.
I've ordered some AB264 and AB263 next time I have a bike set up with O2 meter Im going to do a comparison out of interest

Jugs 
 
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