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crossflow tuning
Trollyjack - 13/4/14 at 08:22 AM

Hi
I'm trying to get my 1300 crossflow to run
having trouble getting it to tick over.
any thing below 1500 rpm and it dies

dont now wheather its carburation or ignition timing.

cannot set dizzy on static timing as i have installed a hall efect dizzy
any one know what advance i should be looking for around 1500rpm.

engine has been fully rebuilt with new pistons over bored to +60"
new gt cam shaft , bearings etc
carb been overhauled and new standard gt jets fitted.

any on any idears

coozer - 13/4/14 at 09:10 AM

I would try a trigger wheel with an Edis and Megajolt...

rusty nuts - 13/4/14 at 09:32 AM

Try advancing the ignition timing, maybe about 15 degrees or so at 1500 rpm , check for air leaks using something like WD40 . Advancing the timing normally gives a slightly higher idle which would help in your case until you get it properly set up .Have you set the valve clearances correctly ? IIRC the GT cam uses different settings to the standard cam

britishtrident - 13/4/14 at 01:16 PM

A bit of common sense guys before jumping to conclusions the first thing to do is clean the idle (what the trade usually call "slow running" jet(s).


Failure to idle with old style carbs is nearly always due to choked idle jets, the idle jets have very small metering holes so get blocked very easily.

Fatgadget - 13/4/14 at 01:36 PM

Xflows and indeed pre-Xflows are indeed as agricultural as engines are.So long as you got a decent spark,good compression,and fueling is sorted,engine WILL run sweet as!

rusty nuts - 13/4/14 at 02:03 PM

quote:
Originally posted by britishtrident
A bit of common sense guys before jumping to conclusions the first thing to do is clean the idle (what the trade usually call "slow running" jet(s).


Failure to idle with old style carbs is nearly always due to choked idle jets, the idle jets have very small metering holes so get blocked very easily.


The original post stated that the carb has been overhauled and new jets fitted, if that haven't been the case I would agree with you

Trollyjack - 13/4/14 at 04:21 PM

so got timing some where near but still will not idle under 1200 rpm
cannot use any fancy ingintion as its being built for locost racing and they dont allow it.

best ive got is to screw the idler jet fully home its a 45 jet and it look like its over fueling.
going to try a 40 jet when i get hold of 1

thanks for your thoughts

jollygreengiant - 13/4/14 at 04:49 PM

quote:
Originally posted by Trollyjack
so got timing some where near but still will not idle under 1200 rpm
cannot use any fancy ingintion as its being built for locost racing and they dont allow it.

best ive got is to screw the idler jet fully home its a 45 jet and it look like its over fueling.
going to try a 40 jet when i get hold of 1

thanks for your thoughts



A, You don't say what carb(s) you are using.

B, Are you adjusting the Idler jet, or, are you adjusting the idle mixture screw. The Idle jet I would normaly assume to be ALWAYS screwed home and would have a sizing. The idle adjustment screw and idle mixture screw are two separate items and normally totally different from the Idle jet.

Just my humble observations.

Trollyjack - 13/4/14 at 07:07 PM

Found the problem

for the last post its a 32 DGV twinchoke

The problem turned out to be as I though over fueling.
when I had rebuild the carb the secondry butterfly was not closing fully thus allowing air to be sucked in concequently also fuel as well.

one I have got it to seat correctly reset the idle jet and the idle screw its fine.