Are there different pilot jets for monoblocs?

[DAVE BRADY]

Hi,

This sounds typical of primary circuit wear.  The tiny air and fuel passageways get eroded over time and cannot be really repaired. No matter how many new bits you fit only the middle and top end can realistically be restored but even then a new slide in a badly worn body will not give optimum results.
I would imagine that a new carb. body with all your new bits fitted will solve any issues and you will get the best from your bike.

Dave.

[highboy_coupe]

Thanks Dave, I agree... I'll start saving my pennies! Unless anyone has a nearly new Monobloc lying around?!

I guess the ultrasonic cleaning would make things worse in this case, as it's removing material and potentially widening any passages. 

[DAVE BRADY]

Hi,

Although ultrasonic cleaning is very good I suspect that even that will not necessarily clean these passage ways.  Once you have the carb sorted you will trouble free riding and the more miles you do the cheaper per miles your new carb body will be.

Dave.

[highboy_coupe]

Oh the saga continues... Put the grotty and suspect 376/8 through the cleaner because why the hell not, and with all the bits swapped onto that body, it starts and idles quite nicely. It does leak from the main jet cover in spite of a new gasket kit from Burlen.
It is much harder to start with the monobloc though, the choke is blocked off but I heard they don't do much anyway.
I can live with the hard starting if "they all do that sir".. as long as it runs nicely out and about and doesn't stall!🤔

[scifi]

The key thing to have an easy starting motor is to get the slow running mixture set perfectly.
Set the throttle stop for a brisker than normal tickover, then adjust the mixture for a peak in rpm.
Reduce the throttle stop to lower the revs back down and repeat the mixture tune again.
When all is OK reduce the throttle stop for the tickover speed you require, competition bikes have to reduce to zero, for safety purposes, and many VMCC members like to reduce to rediculesly low rpm, which I think is just showmanship and not sound engineering.

[DAVE BRADY]

Hi,

Don't forget that the slower the tick over the less the oil flow and pressure so a slow tick over could lead to unnecessary wear especially if pain bearings are involved.

Dave.

[Steve.S]

From what you have said, I believe the solution to your starting problems will be a new carburettor.
In the meantime, regarding the leak, I have found modern fibre washers to be quite useless. Even if softened in acetone, they soon harden up again and leak.
I assume they arrive here on a Container Ship.
Perhaps you might try a Dowty washer, or maybe make a washer out of thickish gasket paper?

[Stubaker58]

It may be that the float bowl lid is buckled, they can be bent back into shape.

[JulianS]

You can get new old stock Monobloc float bowl covers/lids from Autocycle Engineering on ebay/

https://www.ebay.co.uk/itm/265318850347?epid=645125204&hash=item3dc63c5f2b:g:jBkAAOSwdwhgXcwJ

[highboy_coupe]

Thanks for the input, yes I made my own double thick gasket and it is now sealing nicely. I can get it to start quite well on the second "live" kick  after a few priming kicks with the fuel on.

It will idle fine once warm, bit then after a while it will stall, especially at junctions!
I guess clutch drag may not help in first with the clutch pulled in at a junction.

It's strange that idle is more likely to die when fully warmed up!
Yes the answer is probably a new carb, but I'm a sucker for punishment!

[idie]

There is different sizes for monobloc pilot jets. The most used are 20. 25. 30.

[highboy_coupe]

Thanks indie, it's that the one that came in the carb was a different shape, it was marked 20 bit the threaded part was shorter than the one I got from Burlen

[idie]

The most common used size is a 25. 20 is weaker and 30 is richer.