Norfolkluegojnr
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| posted on 21/5/10 at 07:43 AM |
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Thanks Will, we learn't a fair bit in a short space of time.
You've saved the summer! 
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David Jenkins
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| posted on 21/5/10 at 07:53 AM |
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I'm glad it's fixed!
And looking back at what I posted a little while back in this thread...
"Another thought - with my car, it wouldn't go much above 4000 rpm after fitting bike carbs, because it was far too rich at WOT. I reduced
the size of the main jets and it all came together nicely."
<end smug grin...> 
[Edited on 21/5/10 by David Jenkins]
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norfolkluego
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| posted on 22/5/10 at 12:21 AM |
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After Will had sorted the carbs the car really does run well, just one last question. Cylinders 2 and 3 seem to run a bit leaner than cylinders 1 and
4 (no idea why), is it OK to run slightly bigger jets just on 2 and 3 to even things up or should I always run the same jets across all of them, just
pick the best compromise.
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RazMan
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| posted on 22/5/10 at 07:58 AM |
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If the difference between the cylinders is noticeable you should first analyse the rest of the intake & exhaust system. Different length header
pipes, air leaks, airflow turbulence and cylinder temperatures can all cause a slight tolerance in burn quality but how are you determining that there
is a difference? Remember that plug colour is not a true indication of burn quality - the only true way is to use individual Lambda sensors in each
header pipe, which is sometimes used in sophisticated race engines but is normally not required for road engines.
Personally I would get (or borrow) a wideband Lambda sensor and get the overall average of the cylinders and use that for jetting calculation.
[Edited on 22-5-10 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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norfolkluego
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| posted on 22/5/10 at 08:05 PM |
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quote:
Originally posted by RazMan
If the difference between the cylinders is noticeable you should first analyse the rest of the intake & exhaust system. Different length header
pipes, air leaks, airflow turbulence and cylinder temperatures can all cause a slight tolerance in burn quality but how are you determining that there
is a difference? Remember that plug colour is not a true indication of burn quality - the only true way is to use individual Lambda sensors in each
header pipe, which is sometimes used in sophisticated race engines but is normally not required for road engines.
Personally I would get (or borrow) a wideband Lambda sensor and get the overall average of the cylinders and use that for jetting calculation.
[Edited on 22-5-10 by RazMan]
Of all the (possible) causes you mention I would think an air leak on the inlet side would be the most likely, that's definitely worth
checking
[Edited on 22/5/10 by norfolkluego]
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will121
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| posted on 22/5/10 at 09:23 PM |
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hi, some orignal bikes run slightly larger jets in the middle two to the outer ones but this is where standard air box runs different inlet trumpet
lengths and ram air effect may alter individual cylinder fueling. be worth checking for air leaks first and then deciding on what filter arrangements
you going to try as will all potentially effect final jets. from looking at initial filterless plugs going up to 152.5 or 155 may be ok (notice they
on ebay £2.50 each +P&P) ideal is to get a lamba sensor bung welded in manifold to check but if willing to buy a few jets could just try and see
now the filter bowls come off easy!!
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norfolkluego
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| posted on 22/5/10 at 11:42 PM |
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quote:
Originally posted by will121
but if willing to buy a few jets could just try and see now the filter bowls come off easy!!
That's the plan Will. Just try slightly larger jets until it's obvious we've gone too far then go one size back but to be honest
it's running so well at the moment I might just leave it until the end of the summer and just enjoy using it until then. Thanks again for all
your help on Thursday.
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