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123 Right Advance?


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#1 johnR

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Posted 24 June 2019 - 03:10 PM

the default advance on my 123 tune Bluetooth dizzy is:
revs
500 0.0
1000 0.0
1400 7.0
2300 14.6
3500 23.4
5000 29.0
8000 29.0 (rev limit 6k)
The 1293 engine has SW5 cam, ported and large valves,twin HS2s, lighter flywheel.
Does the above curve seem OK to start me off - I seem to be getting a problem at higher revs/on some inclines where it runs very badly/no power for a while then OK again once I've slowed down. I wondered if it might be detonation, but don't know what that's like?

Edited by johnR, 24 June 2019 - 03:11 PM.


#2 ACDodd

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Posted 24 June 2019 - 04:52 PM

Change to curve 6 and set the timing at 10 degrees at idle with the vacuum disconnected And then measure what you have. Reconnect one setting and measurement is complete.

Ac

#3 johnR

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Posted 25 June 2019 - 10:23 AM

I don't think I've got other curves - is that the Tune rather than the Bluetooth dizzy? I'm not sure what what you mean by measuring?
Does it seem likely that the patches of bad running in certain situations is timing related or should I be looking elsewhere?

#4 ACDodd

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Posted 25 June 2019 - 06:18 PM

Whatever dizzy you have needs setting correctly with a strobe light. That advance curve posted above is not optimum for an engine with that spec.

It's very likely you simply need a darn good tune up.

Ac

Edited by ACDodd, 25 June 2019 - 06:23 PM.


#5 johnR

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Posted 25 June 2019 - 09:42 PM

The odd thing is it runs fine until it gets to a certain speed/revs (@ 3500 I think) then clatters like a bag of spoons and loses power for a bit, then once I've slowed down it picks up again as though nothing has happened. I tried backing off the advance a little at those revs - it did seem to improve matters on a local hill where it had been cutting out and I thought I'd solved it. I then took it along a mile long straight and it played up again.



#6 cal844

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Posted 25 June 2019 - 10:05 PM

It sounds like a coil lean fuel mix.... I'd suggest sending the dizzy to AC Dodd or someone equally reputable who can custom tune your dizzy for the application and spec

#7 ACDodd

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Posted 25 June 2019 - 10:27 PM

What's your compression ratio?

Ac

#8 johnR

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Posted 26 June 2019 - 07:07 PM

10:1

Starting to wonder if the fuel pump is up to the job - 30 year old mechanical one from the 998.


Edited by johnR, 26 June 2019 - 09:10 PM.


#9 ACDodd

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Posted 26 June 2019 - 09:44 PM

Easy test, take it for a drive with a fuel pressure gauge plumbed safely into the carb inlet.

Ac




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