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Post by neo on Aug 9, 2016 7:55:17 GMT 1
Just wanted to say that this thread really helped me sort out a similar hesitation issue at 5-6k on my freshly restored 4L0 (well it's actually a 5E0 but same same).
Dropping the needle one notch to second from top and turning the air screws out to 1 1/2 turns has all but cleared up the issue of hesitation and the engine now pulls cleanly right through the rev range, without me having to spend a cent - awesome.
I just wish all forums were as useful as this one, so keep up the good work guys!
Rgds Ozhammer Nice one ozhammer, glad you got yours sorted to! Only another 120 miles until I'm run it 👍
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Post by mags on Oct 14, 2016 19:45:35 GMT 1
Thanks for this thread, glad to hear its possible to eliminate that flatspot, which i used to have and did not find a solution to
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begbie
Drag-strip hero
Posts: 249
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Post by begbie on Oct 15, 2016 14:17:56 GMT 1
Reeds do not need to make an air tight seal, crankcase presure seal the petals against the block.
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Post by hudtm60 on Oct 29, 2016 6:48:51 GMT 1
Neo! Read the thread and realized I'm in the same boat. Got a fully stock 350, been messing with jet's & needles (on 4L0-01s) & airboxes etc and tonight decided to pull the reeds..left hand aren't seating..please have a look at the pics...were yours like these? I hope you can tell...the Top one's gapping....bottom pic- they look ok?
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Post by stusco on Oct 29, 2016 7:39:05 GMT 1
Reeds do not need to make an air tight seal, crankcase presure seal the petals against the block. Open on the way up closed by pressure on the way down doesn't matter if they are gaping slightly
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Post by Bertie Wooster on Oct 29, 2016 17:04:27 GMT 1
Just saw this . I had same thing wrong with mine rather than muck about with second hand reed blocks as you could see daylight through them I took the plunge and bought new ones problem solved 🍺
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Post by hudtm60 on Oct 29, 2016 17:19:57 GMT 1
I asked Norbo about this and he suggested turning around the ones that are slightly gapped at the end. Truth be told if this was the 80's I'd be done at t' Yamaha shop getting new ones, if I could afford it back then (unlikely). Now I can afford it....it's different times...
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Post by 4l04ever on Oct 29, 2016 18:02:13 GMT 1
The hesitation seems to be mainly from too rich fuelling at the 5-6k rev range, so either modifying the airbox, or modifying needle positions or changing needles can change this fuelling to be a little leaner.
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Post by neo on Oct 29, 2016 19:30:01 GMT 1
Just saw this . I had same thing wrong with mine rather than muck about with second hand reed blocks as you could see daylight through them I took the plunge and bought new ones problem solved 🍺 Nice one toonrader glad you got it sorted mine continues to be as smooth as and being all standard I knew it had to be something simple 2 strokes are very sensitive to mixture issues and airleaks.
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Post by neo on Oct 29, 2016 19:33:15 GMT 1
Reeds do not need to make an air tight seal, crankcase presure seal the petals against the block. MATE! Exactly! Great pics! These should be shut tight against the rubber seal or the fuel mixture will be totally wrong and this seems to manifest at 5300 k (ish) possibly all over, these suckeres open and slam thousands of times per minute, wind some new ones in and you will really clean up the throttle response it'll be like a different bike :thumbup:
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Post by rigga on Oct 29, 2016 20:44:35 GMT 1
Reeds do not need to make an air tight seal, crankcase presure seal the petals against the block. MATE! Exactly! Great pics! These should be shut tight against the rubber seal or the fuel mixture will be totally wrong and this seems to manifest at 5300 k (ish) possibly all over, these suckeres open and slam thousands of times per minute, wind some new ones in and you will really clean up the throttle response it'll be like a different bike :thumbup: Unless I'm having a senior moment those two posts completely contradict each other. ....
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Post by neo on Oct 29, 2016 21:14:28 GMT 1
Everyone's bike has their own tailoring needs, mine was duff reeds allowing the wrong mixture. of air /fuel resulting in the hesitation, since I changed them for standard new tight fitting ones it's cured my problem as you said in the post mate everyone's bike is different, if I can share my fix and help others it's all good, asaik reeds have to seal and I thought it was really important to aid smooth running throughout the rev range but I'm learning every day
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Post by neo on Oct 29, 2016 21:19:23 GMT 1
Neo! Read the thread and realized I'm in the same boat. Got a fully stock 350, been messing with jet's & needles (on 4L0-01s) & airboxes etc and tonight decided to pull the reeds..left hand aren't seating..please have a look at the pics...were yours like these? I hope you can tell...the Top one's gapping....bottom pic- they look ok? Mine were also fractured across where they fix to the cage just above the two posi screws, all I can say is that it fixed mine it's so clean now, I replaced mine with brand new standard metal ones and bought some cheap gasket paper from the local auto shop to replicate the gaskets, good luck if you decide to replace and post your results :thumbup:
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Post by hudtm60 on Nov 6, 2016 8:08:26 GMT 1
Fitted new carbon harpowas today but was no t the silver bull let inwas hoping for. If anything the hesitation around the 5300 mark is a little worse - ah well back to messing with the the carburation
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Post by mags on Nov 7, 2016 17:14:16 GMT 1
unlucky, routing for you as this was an issue that plagued my 250 many years ago. sorry i cannot offer any remedybut surprised you have not found your answer here as there are experts aplenty
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