at last: 250 Monza runs nicely

[cooperplace]

I put it all back together yesterday. Fitted a CD ignition. Started and ran almost on the first kick. Runs well. Alternator not charging, so I have to sort that out. No mirrors, so haven't ridden it yet.

[DewCatTea-Bob]

[quote= cooperplace ...
" Runs well.
haven't ridden it yet. "

____ So, have you by-now accumulated any significant millage ?


Duke-Cheers,
-Bob

[cooperplace]

not yet, around the block a few times is all.

[cooperplace]

took it out for a ride this morning, around the block. Started making the most godawful noise just as I got home. Turned out a rear wheel bearing had completely fallen to bits.

Also it doesn't want to idle. I keep on increasing the idle speed, but it still stalls, sometimes going around corners.

I did the valve clearances yesterday: all were very tight, about .005", so I adjusted to the .012" as in the book. Doesn't seem to have made any difference to how it runs.

[DewCatTea-Bob]

[quote= cooperplace ...
" I keep on increasing the idle speed, but it still stalls, "

____ What carb.model do you have installed ?



" I did the valve clearances yesterday: all were very tight, about .005", so I adjusted to the .012" as in the book. "

____ What "book" ? - (Haven't you ever heard-of the warning ? ... viewtopic.php?f=3&t=38 )
__ Doesn't your Duke have a Monza-cyl.head with screw-adjuster type rocker-arms ?



" Doesn't seem to have made any difference to how it runs. "

____ Of-course not to how it 'runs', but you've no-doubt made it a bit more nosier (and possibly also added stress to the operating valve-train).


Dukaddy-DUKEs,
DCT-Bob

[cooperplace]

Hi Bob,
it's got a Mikuni VM26 which the guy at Sudco jetted (hopefully correctly) for a 250. The jet sizes are as published elsewhere on this forum.

Is the .012 size as given the book not correct?

Yes it has screw adjusters.

Thanks again for your advice.

Peter

[DewCatTea-Bob]

quote= cooperplace ...
" it's got a Mikuni VM26 "

____ Sorry, I can't help you with that non-stock carb.model.



" Is the .012 size as given the book not correct? "

____ That's quite-likely rather the particular (excessive) clearance-setting only required just for checking the Monza-type camshaft's valve-timing.



" it has screw adjusters. "

____ Then the intended OPERATING-clearance (between valve-stem & rocker-arm), should rather be just .002" (for intake) & .003" (for exhaust), (although the actual factory-specs [given in metric-figures] may be given within a slightly narrower tolerance-range [than the .001" difference] ). _ In any case, set the intake no tighter than .002" (& up to .0028"), and the exhaust no looser than .003" (& no tighter than .0022").
__ So then, when you had found your valve-clearances near ".005", they were then actually on the loose side, rather than "very tight" !


Dukaddy-DUKEs,
-Bob

[cooperplace]

Hi Bob,

Thanks for pointing out the incorrect specs in some books. I've got what looks like a factory manual which specifies 0.012", but the owners handbook says .005 to .007 mm (= .002 to .0028"). I certainly prefer the advice in the owners handbook. I'll reset accordingly.
Peter

[DewCatTea-Bob]

[quote= cooperplace ...
" Thanks for pointing out the incorrect specs in some books. "

____ Those stated figures actually aren't incorrect, but rather listed within tables which have become mislabeled in newer versions of Clymer Workshop Manuals.



" I've got what looks like a factory manual which specifies 0.012", "

____ Either you've somehow misinterpreted it, or it's not actually a "factory" manual.
__ The valve-clearance figures in question only have to do with checking the valve-timing of the camshaft, and-not the recommended operating-clearance !



" the owners handbook says .005 to .007 mm (= .002 to .0028"). "

____ That's correct, as original-type owner's-manual/handbooks are of-course expected to contain actual factory-specified figures.


DUCATIly,
-Bob