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Tuning a. 28 grp gandini 😠😠

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Old 09-18-2019, 10:50 AM
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Longdogg
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Default Tuning a. 28 grp gandini 😠😠

Hey guys, I could do with some serious help please.
I generally buy slightly beaten up buggies, do them up and sell them on, keeping a couple on the way to bash about with.
Latest one I brought was an ishima rave buggy with a GRP gandini 21 engine in it and a grp 28 engine on its own. On closer inspection of the 21 it was knackered so rather than give up I put the 28 in it as it looked mint condition.
My knowledge is growing all the time but iv read the grp engines are really good but a bugger to tune....
It doesn't like to idle with a standard carb gap, I'm finding that I have to increase it, I can't seem to get the hsn and lsn right either. Has anyone had experience with these engines at all as its driving me crazy.... Any advice is appreciated 👍🏼
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Old 09-25-2019, 08:04 AM
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D3MON
 
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LSN and HSN needles are going to affect the idle quite drastically, have you been able to find factory settings for the needles by any chance? flush on the HSN is typically factory, but some are not. and same with the LSN depending on what the slide looks like.
what kind of sound is the engine making? while running? is it making a chewbacca sound mid/low throttle? if thats the case typically means the LSN is lean. is it giving you a blubbery/throaty sound? are you getting good smoke out of the exhaust at low/mid throttle? high/full throttle?
when it starts with the carb gap opened so wide, is idling high? or is it idling low?
always start with the HSN, get it in the range of a decent tune (make sure it is on the rich side) then go to LSN. tune that really close to where it needs to be then go back to the HSN to finish.
for LSN i will run a few WOT passes then come in and i usually start with the pinch fuel line at the carb then see what it does, i shoot for 3-5 seconds then rev up and die. if it takes longer it needs leaned. shorter- needs to be richer. then to confirm that this is correct, run a few WOT passes, come back in let it sit and idle for about 15 seconds then pin the throttle. if it bogs and dies, still too rich.

Notes:
tune one needle at a time, do not mess with more than one as it can confuse you as to what one actually helped/hurt.
does the idle characteristics change with/without the glow igniter?
what temps are you seeing? (use temps to confirm a good tune, do not tune to temps.)
what fuel are you using? is it fresh?
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