Hi all , and Merry Christmas (Humbug...as said my buddy Dan!).
Back to my Atlas (the N° 2, one ) after months of renovating , she started well with two 30mm concentric, when I decided to fit two monobloc 1 1/8 ,389 and 689, I had found somewhere, they look OK, but missing main jets, and one slide had the small tang where the throttle screw apply , nearly broken (still on but some craks and moving a bit...!), what do you think? as I am more a Commando man, and know nothing about those Monobloc. It appears that the main jet should be in the region of 350and could go up to 420 for the G15....?? though the same design as for the Concentrics, it amazed me !
Should I fit the starter system (I fight with it yesterday evening....!), or like my Commando , could it be left on the bench ...waiting for better days! the float level is it as critical as for concentrics ??
Any advise from the featherbed squadron group , will be wellcome.
Pierre

Monoblocs need relatively more care in rebuilding, and almost ALWAYS need sleeving to carburate cleanly.

The bowl mouths and covers need to be carefully resurfaced or you'll never stop the leaks.

Enrichers work exactly the same, so apply the same logic.

Hymph . Dissagree . IF theyre Mint . Not discarded trash , with warped bodies , scoured bores, warped flanges & stripped
threads .

240 / 250 mains probly on twin carbs . id look at 260 first though .

Generally dont get the Concentric stutter & burrble . Better refinement so better getting underway .No hiss pop fart .

Ow abouta PICTURE ? ? If they are in UNDAMADGED condition ( wear or the like , the adjustments are precise )
Set , slides full open even ( the slide comes down into the top of the bore at the same time / distance.Finger nail )

The old heat insulation flange gaskets , about a eigth thick are usefull . Matched mounting bolts ( OF COURSE )
with Nylock or the Like , LOCKING Nuts , so stay put. DO NOT OVERTIGHTEN . Same with the knurled top lock ring .
Toss worn stretched ones , V fine thread . See its CLEAN .Sit on , EVEN , twist BACK to check even , GENTLY wind
around clockwise . DO NOT FORCE . Itll go on free & easy. Once youve got the bits aligned .

These suckers are probably a good test of a fitters apptitude . A degree of sanity and subtlty is required .
Rather than entusiasm & brute force . The attitude developed is required for the rest of the machine
so is good schooling .
Something these Concentric Blokes miss out on .

Put a Mikuni on it Pierre.
AC.

Matt Spencer wrote:. Dissagree .

What exactly are you disagreeing with?

Monoblocs are excellent carbs if they're properly restored.

Hi, many thanks ,for your different opinions.....but what do you think about the main jets ??? as per the manual and as said above it should be between 350 and 420?? HUGE! isn't it?

Monoblocs use bigger main jets than Concentrics - as a rough guide a Concentric Main Jet is usually around 20% smaller than the Monobloc version for an equivalent engine.

Monoblocks THAT Dont Need Restoring , are Excellent Carbs .

Cant see it worth the TROUBLE ( potential catastrophic & niggling ) to rebuild ANY carb with a DAMADGE houseing / body .

second best isnt good enough . Good way to ruin a fresh engine . seeing NEW ones are available , the limits are Endless .

A monoblock should give superior low range accuracy to about anything , or Equal . If its not a Raceing Engine .

I leave the Jap bits to the Jap bikes . No point in makeing its parantage questionabe . .

If the Bodies Buggerd , toss it , or Find a LARGE Hammer , and give it a Good ' Tap ' .

P.S. I throw out the Cold Start system , unless its snowing and you dont know how to hold the Throttle Open .
A Monoblock with idle scew backed of so as slide closes entirely will give better accuracy stealing the Apex
leaveing hondas behind in the mountains .

marinatlas wrote:Hi, many thanks ,for your different opinions.....but what do you think about the main jets ??? as per the manual and as said above it should be between 350 and 420?? HUGE! isn't it?

THATS for the SuperCharged Version . ! ( )

I believe those giant size jets are for pre-mixed 2-stroke fuel.

The Atlas is listed as having jets in the 400 range with monoblocs.

Wasn't there something about monoblocs flowing/feeding the fuel differently, or something. Huge jets didn't give huge fuel consumption...

May have to do with the slide cutaway...