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preignition!!!!


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#1 stevenford_uk

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Posted 19 January 2004 - 01:29 PM

filled me mini thou up with unleaded the other day, its an 86, done 68000 miles, and when i turn it off it preignites like fcuk and keeps running for bout 10 seconds after turning it off. what can i do?

#2 Bluemini

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Posted 19 January 2004 - 10:39 PM

Go back to using full fat, unleaded is cack...
You can get around the over-run by adjusting the timing slightly. If you have a timing light, look to see were the timing is now, then adjust it slightly advanced or retard (cant remember wich way!). Loosen the dizzy and turn it a tiny amount, and i mean a tiny amount and try it, if its no better, try it a bit more and so on. If you aint got a light, then mark the dizzy and were it touches the block so you've got a refrance point, then turn it a fraction either way till its ok.

#3 bumblebee

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Posted 21 January 2004 - 07:53 PM

turn the engine off 10 secs before you intend to, problem solved, seriously tho, timing is the answer!, i use a castrol fuel additive, it adds lead to the petrol and boosts octane, a fiver a bottle, does bout 150 quid of petrol too

#4 stevenford_uk

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Posted 22 January 2004 - 10:47 AM

i am now using optimax, but its no better, and when the thing is cold it misfires like :) and preignites like a b****rd when i put my toe down at all, will be avin a look at the timing tomorrow.

#5 Bluemini

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Posted 22 January 2004 - 07:02 PM

Take the dashpot off and give it a service, take it all apart and clean it with thinners, put it back on and put in some 3 in 1 oil in the dashpot and see if that helps...

#6 stevenford_uk

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Posted 23 January 2004 - 01:03 PM

by dashpot you mean the bowl shaped thing on top of the carb?
the carb is not std, the carb is an hif44!!! on a thou!!!
the previous owner thought it would be a great idea to put this sod off great carb on it, it now runs rich as hell, like C**p, misfires, and everything! am i best just gettin an lcb, alloy inlet and an inch and half su or inch and a quarter? but to try and cure the preignition, just give the thing a thorough service?

#7 David_J

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Posted 03 February 2004 - 12:24 PM

Don't know about the carb being too big but as far as timing goes you need to retard it for unleaded.
To tune the set up roughly you can just advance it in stages until it starts pinking when you floor it in third gear under load then retard it gradually until it stops pinking under the same conditions.
Advancing is turning the dizzy body in the opposite direction to the rotation of the rotor arm. Retarding is t'other way around.

#8 Bluemini

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Posted 03 February 2004 - 06:24 PM

Might be worth getting an 1 1/2" carb too because the one you got on it now is a major overkill and wont be doing it any favours or good...

#9 stevenford_uk

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Posted 05 February 2004 - 09:47 AM

i have now got it running sweet as hell!
the carb appears to be jetted correctly! it runs lean without the airfilter on, with the std air filter on it runs really well.
changed the HT leads for race jobbies and they are awesome, all the pinking has stopped, it goes shitloads better, and its now great on fuel! to £10 i am getting between 85-100 miles depending on driving and conditions!!!
it has no more misfires, i love it now!

#10 Bluemini

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Posted 05 February 2004 - 06:21 PM

Glad to hear it. Dont you jus love it when a plan comes together... lol




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