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RE: General Motorhead Questions, I Think

To: "'triumphs@autox.team.net'" <triumphs@Autox.Team.Net>, "'Jackson, Dee'" <Dee_Jackson@gilbarco.com>
Subject: RE: General Motorhead Questions, I Think
From: Gernot Vonhoegen <gernot.vonhoegen@stir.ac.uk>
Date: Tue, 10 Nov 1998 15:15:44 -0000
judging from what you say you are not running too lean but you are running
too rich. What happens if you lift the piston is that a thinner section of
the needle is exposed, thus more petrol comes in. As its already running
rich it dies. check the plugs after you have run the engine for a time. They
should be brown wehen the engine is warm. If you find black plugs you are
running too rich, grey ones indicate lean running (that of course is only
valid when you run the correct plugs. PLus it only is valid for the given
rpms.
A colourtune will be of good value when you are a novice as this makes
things pretty easy. As well check that the carbs are synchronised as th9is
might cause your hunting as well. 

> ----------
> From:         Jackson, Dee[SMTP:Dee_Jackson@gilbarco.com]
> Reply To:     Jackson, Dee
> Sent:         Tuesday, November 10, 1998 2:37 PM
> To:   'triumphs@autox.team.net'
> Subject:      General Motorhead Questions, I Think
> 
> The machinist made a few performance mods on the head (port matching,
> removing the rough stuff in the exhaust ports and lightly unshrouded the
> valves) and took off .010 to make it flat.  I put in a hotter cam (.415
> lift, 270 duration) and a header and  am running the stock CD150 carbs.
> On starting it up for the first time, it ran pretty roughly, which I
> expected, but I couldn't get it to idle at anything below 1500 rpm.
> Thinking I had a vacuum leak somewhere I began spraying carb cleaner to
> try to find it.  Spraying around the throttle spindles yielded a
> noticeable increase in rpm, so I sent them off to Apple Hydraulics for a
> complete rebuild.   They came back in a week (and look great), but I'm
> still having a problem getting an acceptable idle.  I was told by the
> cam supplier that I should be able to have a smooth idle at 900 rpm.  I
> can't get close to that, it's more like 1200 and it hunts at idle.
> 
> In trying to dial in the carbs, I've turned the needles to the max rich
> position, but if the throats of the carbs are partially blocked with my
> hands there is an increase in rpm.  Lifting the pistons 1/16 inch causes
> the engine to die.   Putting a Unisyn over the throats also causes an
> increase in rpm.  I think this is a case of still being too lean.
> 
> At this point, I have checked the points gap, verified the timing with a
> strobe light, made sure the cam was set at the right point (#1 intake
> max open @112 degrees ATDC) and sprayed carb cleaner around the intake
> manifold to check for leaks (can't find any).  I've plugged the vacuum
> advance port on the rear carb and am venting the rocker cover directly
> to both carbs via a tee-fitting with no emissions control valve.  My
> plans this weekend are to take off the intake and header and look at the
> gasket to see if there is any sign of a leak there and check the valve
> clearances again, assuming there aren't too many honey-dos from the
> wife.   
> 
> Is it typical to have to run smaller needles to account for the cam and
> header, or am I a classic case of a little knowledge being a dangerous
> thing, or both?   Have I missed anything?
> 
> Thanks for any advice you can offer.
> 
> D.
> Spit FM90204UO
> GT6 KF20632U
> 

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