Monty carbs

S

SeeDoubleYou

Junior member
So to the next issue now the plugs are sorted. The bike has PHF carbs with what looks like standard jets. The bike won?t rev over 6,000rpm however. I?m going to do another full strip and clean tomorrow, however I?ve never been any good with carbs so can somebody give me a clue what this might be or where to look first.
 
Hi,
Can you tell us what size jets are in the carbs?
Standard original exhaust?
What plugs you running.
Standard original ignition system?

Etc Etc

Andy
 
Sorry of course. Standard ignition, Sito pipes, NGK 9s. The mains I?ve tried several and it makes no difference. The Monty part list shows a 140 main which is a lot bigger than the Alpino. Top of my head I think I?ve been through 138 down to a a 130. I?ll have to look where I finished off tomorrow.
 
Just to add, my thinking is that at about 6k I?m guessing it should come onto the main jet circuit so I was womdering if something was wrong with one of the other carb curcuits
 
Revs have no bearing on main jet - it's determined by throttle position - from 3/4 to full throttle. Anything below that will be controlled by things like needle and needle jet.

Having said that, if needles have been swapped out for different profile (ie thicker at the tapered end), it can limit the amount of fuel that can pass when onto the main jet circuit.
 
Lack of fuel at higher revs sort of point to float levels being too low or not enough flow through the petcock. Does it run well below 6k?
 
Hi,
Do the slides move all the way up the body of the carbs?

Choke plungers seating correctly?

How does it run below 6000? Does it start without any choke?

Andy
 
Hi. It runs spot on below 6k. I use a bit of choke to start and then it runs evenly once the choke is engaged. Picks up ok through the gears and then, as you say, I get to about3/4 throttle and nothing. I have a spare set of carbs I can build up and try in an effort to eliminate the problem but wondered if anyone had any other advice other than the good stuff given just here.
 
Maybe check fuel flow from the taps, could be starved of fuel.Try opening the tank cap as well, vapour lock from the cap breather. What air filter, try it without one
 
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