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Post by Tobyjugs on Jan 27, 2017 22:12:37 GMT 1
I am trying to adjust my Standard size 4LO 00 carbs and i have come to a point where i think the mixture is still too weak and if i put in a 460 or a 500 main jet in there is no difference in performance seen on a dyno ( i was trying to find the point where the power dropped because it was too rich) without co2 sensor. Is it possible that the needle jets are too small? or is it time to get bigger carbs? Thanks Tobyjugs
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Post by jon on Jan 28, 2017 8:18:32 GMT 1
Tobyjugs, out of interest are your carbs pre or post mod?
Jon
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Post by Tobyjugs on Jan 28, 2017 16:07:30 GMT 1
Hi Jon i have no idea. Pieter the tuner has explained to me it was all to do with area of the needle and the jet which when calculated were almost the same. I think it is time to get in touch with Topham Mikuni and ask them. I also have some 250 needles 5GN36 i will try as they are more tapered compared to the 5K1 needles that i have always used.
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Post by Tobyjugs on Jan 30, 2017 17:01:37 GMT 1
I have been given three pieces of advice. Reduce air flow through the filter. (last resort} Change size of air jet in the carbs. (sounds like a lot of work) Grind the end of the needle down. (sounds like fun) Tomorrow i will sacrafice 2 needles to the god of speed. (wish me luck)
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Post by bare on Jan 30, 2017 21:03:25 GMT 1
yikes! 460 - 500's. Might just as well run a straight fuel line, seems a wee bit OTT.
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YZR654
L plate rider.
Posts: 44
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Post by YZR654 on Jan 30, 2017 21:16:40 GMT 1
this may help you if you take out the main jets and run it without them and it is the same it means the needle jet, (not the needle) is to small, if it runs rich it is ok you can then try different main jets till you get it right. changing to larger main jets and it makes no difference means the needle jet is to small, do not cut down the needles ever that will not work
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Post by Tobyjugs on Jan 30, 2017 21:40:30 GMT 1
this may help you if you take out the main jets and run it without them and it is the same it means the needle jet, (not the needle) is to small, if it runs rich it is ok you can then try different main jets till you get it right. changing to larger main jets and it makes no difference means the needle jet is to small, do not cut down the needles ever that will not work Thanks for giving good advice never thought about that and it make sense. I was thinking about altering the last piece of the taper, but first i will do what you suggested as i was also wondering about enough flow through the needle valves. Cheers for that PS welcome to the forum
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Post by Tobyjugs on Jan 30, 2017 21:49:57 GMT 1
Thanks Tony i have the manual and read it but to be honest i think 70+ hp is getting to the limit of standard carbs
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YZR654
L plate rider.
Posts: 44
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Post by YZR654 on Jan 30, 2017 22:03:01 GMT 1
yes 70 ponies is a lot sounds like the best thing is bigger carbs possibly 32mm. I have 4 32mm TMs on my yzr biaggi replica which has 350ypvs barrels and heads and that runs really well but they are quite big, don't know if you will have the room, good luck
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Post by Tobyjugs on Jan 30, 2017 22:07:25 GMT 1
yes 70 ponies is a lot sounds like the best thing is bigger carbs possibly 32mm. I have 4 32mm TMs on my yzr biaggi replica which has 350ypvs barrels and heads and that runs really well but they are quite big, don't know if you will have the room, good luck Sounds interesting what pipes you using
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Post by Tobyjugs on Jan 30, 2017 22:28:37 GMT 1
Yeah your both right, i just like to use what i've, i have got some old tz power jet carbs if push come to shove i will begin to fit them (They look clean but i don't have xray eyes) and then i have to go back on that learning curve to try and adjust them. Where as ive got a bit of an understanding of jetting of these carbs and in two weeks from now i want to use the bike.
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YZR654
L plate rider.
Posts: 44
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Post by YZR654 on Jan 30, 2017 23:54:37 GMT 1
the whole bike has been built by myself including the pipes, it took 2 years and a lot of work and thought as I wanted it to work well on the road, I am pleased to say it does, but still have many things I want to do to it, will post some pics soon
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Post by bare on Jan 31, 2017 18:49:21 GMT 1
Note that 'bigger' carbs float bowls foul the clutch lever. Some have 'solved' this by mounting their carbs askew in the inlet rubbers. . (yes it has worked.. even on successful race bikes). While most opt for a bespoke intake manifold.. $$.
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Post by marsbar350 on Jan 31, 2017 18:56:40 GMT 1
got PWK 28s on my Athena barrels produce 75 bhp and 44 ftlbs of torque had to remove fuel filters as it wasn't getting enough
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Post by wallcraft on Jan 31, 2017 19:39:37 GMT 1
got PWK 28s on my Athena barrels produce 75 bhp and 44 ftlbs of torque had to remove fuel filters as it wasn't getting enough What exhausts are you using?
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Post by marsbar350 on Jan 31, 2017 19:40:58 GMT 1
got PWK 28s on my Athena barrels produce 75 bhp and 44 ftlbs of torque had to remove fuel filters as it wasn't getting enough What exhausts are you using? kennys
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Post by Tobyjugs on Jan 31, 2017 21:09:55 GMT 1
Ok back home relieved with a smile. It turned out that the problem was indeed the size of the needle valves. About half a year ago i ordered some new needles and needle valves for these carbs and i must of just fitted them without checking them because they were P0 345 needle jets instead of P2 345 needle jets the p2's are bigger. So now the engine is running rich which is nice and safe and its kicking out 68 hp.
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Post by Tobyjugs on Jan 31, 2017 21:14:30 GMT 1
got PWK 28s on my Athena barrels produce 75 bhp and 44 ftlbs of torque had to remove fuel filters as it wasn't getting enough What exhausts are you using? I am using exhausts made by Pieter Smidt from PS Tuning
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Post by Tobyjugs on Jan 31, 2017 21:18:30 GMT 1
got PWK 28s on my Athena barrels produce 75 bhp and 44 ftlbs of torque had to remove fuel filters as it wasn't getting enough The engine is making 68hp and 52nm of torque. I have had bad experiances with fuel filters so don't use any. I prefer to clean the carbs out. But all my tanks are clean.
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Post by Tobyjugs on Jan 31, 2017 21:35:57 GMT 1
I have got a pair of TSA's for my other bike but when i fitted them the bike was mad and i never had any jets big enough. I then put the PS's on and i could jet it. I put the original filter housing back on but found it difficult to jet and it had a stutter between 6000 and 6500 rpm which i did not like. This one will also be on the dyno Shortly with with pods and TSA's
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Post by marsbar350 on Jan 31, 2017 21:41:04 GMT 1
my carbs and tank had very fine rust particles in.anyway all good now I run stock airbox with drilled lid fosm filters make way harder to set up whats this 53nm? how do you convert to ftlbs
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Post by Tobyjugs on Jan 31, 2017 21:54:54 GMT 1
my carbs and tank had very fine rust particles in.anyway all good now I run stock airbox with drilled lid fosm filters make way harder to set up whats this 53nm? how do you convert to ftlbs As a rough guide take one third off. It is actually 39 ftlbs. how many CC's is your engine?
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Post by marsbar350 on Jan 31, 2017 21:57:36 GMT 1
my carbs and tank had very fine rust particles in.anyway all good now I run stock airbox with drilled lid fosm filters make way harder to set up whats this 53nm? how do you convert to ftlbs As a rough guide take one third off. It is actually 39 ftlbs. how many CC's is your engine? 3**
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Post by Tobyjugs on Jan 31, 2017 22:05:11 GMT 1
Ahh the same as mine sensible choice. I wont tell my mate because he is in love with the Athena kit
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Post by Tobyjugs on Jan 31, 2017 23:53:06 GMT 1
Ah, Schoolboy error with the needle jet, Glad you got it sorted now Yes look before you leap
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