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Post by JonW on Nov 11, 2021 12:45:22 GMT 1
Bugger, me never checked for any other writing, only saw the Mikuni logo then N-8 Have you spoke to Allens Performance They supplied me with the needles and nozzles for the 250 Steve Haha, lol. the shorter codes usually have numbers as well No, not exactly easy to get in touch with from here ive found. they seem to like a phone call which isnt ideal lol
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Post by JonW on Nov 11, 2021 12:46:33 GMT 1
Hi John I don't have much info for you a customer told him his bike was running badly. It kept cutting out on one cylinder if more than 7000rpm. After a lot of checking he found the problem. The owner drilled open the jet because it was blocked. He just fitted another jet and reamed it out to the size of the jet in the other bowl. This solved the problem. Ahh ok, that makes sense. I'll see if Dave can shed any light on this as he might have experience with these carbs.
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Post by muttsnuts on Nov 11, 2021 18:53:10 GMT 1
LOL - just seen this thread - made me laugh alot !
Ok, so the 1XA carbs are an interesting setup, the fixed PJ are very small, around 30 in size, iirc one is 30 and the other 35, but they are fixed. The needle jet is the same as the 1UA carb, the main and pilots are generally different, by one size I think, I'd need to check. The 5L20 needle is required with the needle jet (N-8) as that needle jet is a 2 paired hole jet (544 series), same as in the 1UA carbs
The needle jets in the 31K carbs are the 345 series (P2), these have 5 paired holes and must be run with the 5K1 needle, or at least with the 5K series needles, you shouldn't use them with the 5L, 4N or 4H series needles.
The internal drillings on the 1XA carbs are pretty identical to the 1UA, but again iirc the air corrector is a different size, 0.6mm instead of 0.8mm
To the question of the PJ in the float bowl, these are very specific jets (BS30/97), they are different to pilots (4mm x 5.5mm long) in both size and design, they are more akin with air jets used in the later Mikuni series carbs like TM's and the likes. They are 4mm thread by 7.5mm long and you can drill the fixed ones out and tap the spigot with a 4mm thread and then fit the PJ jets, but you need to be careful not to drill and tap too deep into the bowl as otherwise you'll screw up the vacuum/draw length and the PJ won't work correctly.
You can make the 1XA carbs work fine on a 350 by just jetting it the same as the 1UA (use 1UA) parts etc and it will be pretty damn close, if anything I think the 1XA carb is better than the 1UA carb, but that might be just because they seem to be in better shape normally
Anyway, hope that helps !
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Post by JonW on Nov 11, 2021 23:26:44 GMT 1
Thanks for your post Dave. Glad we made you laugh. Very interesting info. I'll reread what youve posted oce Ive woken (after a big coffee). I agree re the condition, its really good on these carbs.
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Post by JonW on Nov 12, 2021 9:06:31 GMT 1
LOL - just seen this thread - made me laugh alot ! Ok, so the 1XA carbs are an interesting setup, the fixed PJ are very small, around 30 in size, iirc one is 30 and the other 35, but they are fixed. The needle jet is the same as the 1UA carb, the main and pilots are generally different, by one size I think, I'd need to check. The 5L20 needle is required with the needle jet (N-8) as that needle jet is a 2 paired hole jet (544 series), same as in the 1UA carbs The needle jets in the 31K carbs are the 345 series (P2), these have 5 paired holes and must be run with the 5K1 needle, or at least with the 5K series needles, you shouldn't use them with the 5L, 4N or 4H series needles. The internal drillings on the 1XA carbs are pretty identical to the 1UA, but again iirc the air corrector is a different size, 0.6mm instead of 0.8mm To the question of the PJ in the float bowl, these are very specific jets (BS30/97), they are different to pilots (4mm x 5.5mm long) in both size and design, they are more akin with air jets used in the later Mikuni series carbs like TM's and the likes. They are 4mm thread by 7.5mm long and you can drill the fixed ones out and tap the spigot with a 4mm thread and then fit the PJ jets, but you need to be careful not to drill and tap too deep into the bowl as otherwise you'll screw up the vacuum/draw length and the PJ won't work correctly. You can make the 1XA carbs work fine on a 350 by just jetting it the same as the 1UA (use 1UA) parts etc and it will be pretty damn close, if anything I think the 1XA carb is better than the 1UA carb, but that might be just because they seem to be in better shape normally Anyway, hope that helps ! Dave, Great info... a couple of questions: 1, do you know why one side has a larger size than the other? And also which is the bigger size? 2, FYI the p345-2 is the emulsion for the 1GA 250 carbs, it is paired from the factory with 4N10 needles. Doesnt the 4L0 have a 345-0 Emulsion? 3, Interesting about the drillings... Do you know where this drilling is sited? 4, When you say you can just fit the 1UA jetting to get a 1XA to run 'as a 1UA', I assume you mean all of the jets including the bowl and the main / pilots and not just making the main jet larger and using the 1UA pilot size? 5, I assume the PJ in the bowl has more 'function' than just splitting the total jetting across the two circuits... ie there is more magic going on than that?
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Post by muttsnuts on Nov 12, 2021 12:15:01 GMT 1
LOL - just seen this thread - made me laugh alot ! Ok, so the 1XA carbs are an interesting setup, the fixed PJ are very small, around 30 in size, iirc one is 30 and the other 35, but they are fixed. The needle jet is the same as the 1UA carb, the main and pilots are generally different, by one size I think, I'd need to check. The 5L20 needle is required with the needle jet (N-8) as that needle jet is a 2 paired hole jet (544 series), same as in the 1UA carbs The needle jets in the 31K carbs are the 345 series (P2), these have 5 paired holes and must be run with the 5K1 needle, or at least with the 5K series needles, you shouldn't use them with the 5L, 4N or 4H series needles. The internal drillings on the 1XA carbs are pretty identical to the 1UA, but again iirc the air corrector is a different size, 0.6mm instead of 0.8mm To the question of the PJ in the float bowl, these are very specific jets (BS30/97), they are different to pilots (4mm x 5.5mm long) in both size and design, they are more akin with air jets used in the later Mikuni series carbs like TM's and the likes. They are 4mm thread by 7.5mm long and you can drill the fixed ones out and tap the spigot with a 4mm thread and then fit the PJ jets, but you need to be careful not to drill and tap too deep into the bowl as otherwise you'll screw up the vacuum/draw length and the PJ won't work correctly. You can make the 1XA carbs work fine on a 350 by just jetting it the same as the 1UA (use 1UA) parts etc and it will be pretty damn close, if anything I think the 1XA carb is better than the 1UA carb, but that might be just because they seem to be in better shape normally Anyway, hope that helps ! Dave, Great info... a couple of questions: 1, do you know why one side has a larger size than the other? And also which is the bigger size? - choke side is bigger, the reason its bigger is because of the choke circuit, that carb has a couple of extra holes in it for the choke circuit, so on WOT extra air is drawn in, also note that the correcrt PJ sizes are RHS 50, LHS 552, FYI the p345-2 is the emulsion for the 1GA 250 carbs, it is paired from the factory with 4N10 needles. Doesnt the 4L0 have a 345-0 Emulsion? - yes the 4L0 runs a 345-0, or a 345-p2, depends on the year !, you can run any 345 series, you'd just need to play with the needles to make them work - the 250's require different fuelling, I'd assumed we was talking 350's, saying that, I've seen needles that don't supposedly mix well with needle jets work really well - but you need to check the fuelling across the rev range to be sure it doesn't lean out or richen up too much at certain RPM - this is where having a dyno with O2 sensors becomes invaluable - you can't gauge the fuelling on an unloaded engine3, Interesting about the drillings... Do you know where this drilling is sited? - just the air corrector is the one to account for, again it can be worked around once you have the O2 readings4, When you say you can just fit the 1UA jetting to get a 1XA to run 'as a 1UA', I assume you mean all of the jets including the bowl and the main / pilots and not just making the main jet larger and using the 1UA pilot size? - correct, make it identical, usually get the air correction sorted by using a combination of the air screw and the needle position
5, I assume the PJ in the bowl has more 'function' than just splitting the total jetting across the two circuits... ie there is more magic going on than that? - yes, the PJ's only really start to work on maximum engine "suction", this doesn't necessarily equate to maximum rev's, its how much vacuum is being subjected to the PJ outlet, hence why the "air gap" distance is so important, if the jet is too low and you won't draw enough fuel, too high and you'll draw fuel at the wrong time and too much of itsee my comments next to yout questions above
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Post by JonW on Nov 12, 2021 12:40:48 GMT 1
Dave, Great info... a couple of questions: 1, do you know why one side has a larger size than the other? And also which is the bigger size? - choke side is bigger, the reason its bigger is because of the choke circuit, that carb has a couple of extra holes in it for the choke circuit, so on WOT extra air is drawn in, also note that the correcrt PJ sizes are RHS 50, LHS 552, FYI the p345-2 is the emulsion for the 1GA 250 carbs, it is paired from the factory with 4N10 needles. Doesnt the 4L0 have a 345-0 Emulsion? - yes the 4L0 runs a 345-0, or a 345-p2, depends on the year !, you can run any 345 series, you'd just need to play with the needles to make them work - the 250's require different fuelling, I'd assumed we was talking 350's, saying that, I've seen needles that don't supposedly mix well with needle jets work really well - but you need to check the fuelling across the rev range to be sure it doesn't lean out or richen up too much at certain RPM - this is where having a dyno with O2 sensors becomes invaluable - you can't gauge the fuelling on an unloaded engine3, Interesting about the drillings... Do you know where this drilling is sited? - just the air corrector is the one to account for, again it can be worked around once you have the O2 readings4, When you say you can just fit the 1UA jetting to get a 1XA to run 'as a 1UA', I assume you mean all of the jets including the bowl and the main / pilots and not just making the main jet larger and using the 1UA pilot size? - correct, make it identical, usually get the air correction sorted by using a combination of the air screw and the needle position
5, I assume the PJ in the bowl has more 'function' than just splitting the total jetting across the two circuits... ie there is more magic going on than that? - yes, the PJ's only really start to work on maximum engine "suction", this doesn't necessarily equate to maximum rev's, its how much vacuum is being subjected to the PJ outlet, hence why the "air gap" distance is so important, if the jet is too low and you won't draw enough fuel, too high and you'll draw fuel at the wrong time and too much of itsee my comments next to yout questions above Fantastic info Dave, Thank you so much. 1 more... Are the early 4L0 carbs the P345-2 version and the -0 the later ones?
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Post by muttsnuts on Nov 12, 2021 12:46:00 GMT 1
see my comments next to yout questions above Fantastic info Dave, Thank you so much. 1 more... Are the early 4L0 carbs the P345-2 version and the -0 the later ones? T he early carbs are 0-6 needle jets (same needle jet as the 250 ironically) with a 4H16 needle, the later carb 4L0-01 is 345-p2 and the 5K1 needle, the 5K1 needle is approx 2mm longer the 4H16 needle iirc, hence why you can't mix and match them, plus the 3 tapers on the neelde are very different
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Post by muttsnuts on Nov 12, 2021 12:53:32 GMT 1
one thing not mentioned, and most people forget, is that the reed blocks and petals where changed (kept the same part number) when the carb upgrade/mod came out and where fitted to all 81 models onwards, this affects the fuelling massively and is why so many LC's have mid range stutters, even though they are jetted according to the book, the early reed petals where much stiffer, which affects how the fuel is drawn into the engine and at what RPM it occurs, clearly a stiffer petal means less fuel is drawn into the engine at a given RPM, a weaker petal opens sooner and therefore subjects the carb to more "draw", which in turn pulls more fuel into the engine, ironically the mid range stutter everybody says "they are all like that" is generally caused by this mismatch and the only way to fix it is to tweak the carbs.
Of course there is much more going on as well and I can't give all of my secrets out (I'd be out of business!) but the 2T engine has to have all of the requisite parts configured and working with each other, just one wrong part screws it all up
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Post by JonW on Nov 12, 2021 13:17:43 GMT 1
Fantastic info Dave, Thank you so much. 1 more... Are the early 4L0 carbs the P345-2 version and the -0 the later ones? T he early carbs are 0-6 needle jets (same needle jet as the 250 ironically) with a 4H16 needle, the later carb 4L0-01 is 345-p2 and the 5K1 needle, the 5K1 needle is approx 2mm longer the 4H16 needle iirc, hence why you can't mix and match them, plus the 3 tapers on the neelde are very differentCool, ta for that. I will check my 4L0 setup when i next put it on the lift
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