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Post by dougw on Mar 14, 2021 17:40:59 GMT 1
Hi, got the original 4l00 carbs, modified.
4 to 6K flat spot
Cleaned air corrector jet behind modified blanking plug, cleaned emulsion tube, changed 180 mains it came with to 170s, new throttle cable to synchronise throttles, it’s getting better.
Marked throttle tube up today, it’s still rich four stroking at half throttle, so next step dropping needles from position 3 to position 2.
Will then be set to Yamaha settings “ for continuous high speed use “ , I think.
Eventually getting round to a question, looking at getting new needles and emulsion tubes from Allen’s, Haynes states 4H16 needle and 0-6 needle jet, are these the best options ?
Off to check now what is actually available from Allen’s.
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Post by andy748 on Mar 14, 2021 18:38:54 GMT 1
I would try going up one size or possibly two on the pilots with the 170s first. Andy.
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Post by dougw on Mar 14, 2021 18:53:26 GMT 1
I would try going up one size or possibly two on the pilots with the 170s first. Andy. Plugs are totally black, it’s very rich at half throttle, runs fine tickover to 1/4 throttle, why bigger pilots ? |
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Post by andy748 on Mar 14, 2021 19:11:47 GMT 1
After watching Dave set an LC up on the dyno, the pilots make a big difference between 4-6k, but going bigger generaly means lower main jet size, worth trying for little outlay? I'm sure Dave will be along at some point to advise! Andy.
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Post by dougw on Mar 14, 2021 19:25:33 GMT 1
Hmm. Its running 27.5 pilots now, tried it with 22.5 and it ran slightly better at 4 to 6, but worse up to 3000, feeling lean.
While nothing would surprise me with fickle two strokes, I can't understand how adding more fuel would help if its very rich ?
I'm fairly sure I'm not going to get rid of the mid range flat spot until I have my dodgy porting sorted out, but as its a fresh build want to get it as good as possible while getting a few hundred miles on the bores.
Appreciate the comments,as you said , may be worth a try.
Edit to add, its supposed to have a 160 main , so It's already 10 up on that.
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Post by bare on Mar 22, 2021 16:41:42 GMT 1
.. Buy cheap = Buy twice and if Dim .. repeatedly.
Trite but Ohhh so true.
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Post by dougw on Mar 22, 2021 17:57:43 GMT 1
Not quite sure what relevance Buy Cheap has to current project, not sure what others consider cheap ,£50 for a new set of genuine needles and needle jets didn't seem cheep to me !
It has made a difference though.
Leaving the new needles on the lowest notch, which used to be still rich, its now lean. (All new genuine Mikuni jets now).
Slow but steadily improving.
Tonight's jobs put new needles on notch 3 as per Yamaha dealer mod.
Test ride.
Make plug hole adapter for dial gauge as can`t find mine, last used circa 1993 , 4 houses ago.
Search for timing strobe light(s).
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Post by dougw on Mar 22, 2021 18:02:51 GMT 1
After porting sorted new ignition, zeel or ignitech and new coils will be next on list.
Want to make sure everything existing is set up as good as possible and not just bolting on stuff to something that is not correct.
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