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rebore
Aug 28, 2013 16:18:59 GMT 1
Post by thehut on Aug 28, 2013 16:18:59 GMT 1
after a engine has had rebore. on my rd350lc do you need to go up a size on jets from standard. been on all day moving air screw and dont seem to be able to stop it running on weak side. plugs are grey but dont burn the plating of outside ring. bike does about 70 max. it got quite a bit stutter and hesitation to. till it hits powerband
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rebore
Aug 28, 2013 16:55:03 GMT 1
via mobile
Post by davey on Aug 28, 2013 16:55:03 GMT 1
Try droping the circlip a notch or two on the needles so in essence lifting the needle , this will richen the mixture. Also try screwing out the air mixture half a turn as this will make it richer on tickover. I never heard of having to rejet after a rebore but no doubt some one here will have more info than i regarding that.
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rebore
Aug 28, 2013 17:39:11 GMT 1
Post by arrow on Aug 28, 2013 17:39:11 GMT 1
Should be fine standard, suspect its got an air leak somewhere. Mine has the weak stutter you speak off bit only when its cold, a quick touch of choke is all that's needed to cure. No issues when warm when the mixture is then correct.
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rebore
Aug 28, 2013 17:47:07 GMT 1
Post by muttsnuts on Aug 28, 2013 17:47:07 GMT 1
I tend to up jet to 230's from 220's (if 4L0 01 carbs) if I can't get it with lifting the needles up (assuming you are running a standard airbox etc).
The bigger main jet tends to make it rich, but then it means I can play with the needle quite a bit and also means if spannies are fitted I am already on the right side of jetting for the extra free flowing exhausts.
As a general guide (and it is general), if you have to turn the air screw in fully then the pilot jet is too small, if you have to turn it out more than 4 turns then its too big, but you need to keep in mind that is all in relation to the size of the main jet and also the needle position, it can be a fine line getting them all aligned/set up correctly, it also depends on what version of carbs and any mod's that have been done to them, they do vary quite a lot so you do need to know this info
By way of example, I had an RD400F in at the weekend, it ran very well, but had a slight stutter at 4.5k rpm to 5k rpm, on the dyno it was running fine, although it was a little weak mid range and at the very top of the rev's (9k), it was making 44bhp.
After some fiddling and other checks, I changed the main jet from a 155 (standard is 145) to a 160, this made it better and cleared the stutter after we adjusted the needle position and air screws etc, it was now making 50.4bhp, however, at 9K rev's it was reading ok on the fuel air, but a little close to the red zone (more than I like anyway), so did a plug chop, this showed it was running just a tad weak.
I changed the main to a 165, dropped the needle 1 clip position, turned the air screws out 3 turns and re-ran it, it was now making 49.4bhp, so a slight drop, but the fuel/air ratio was much more in the safe zone, a further plug chop showed a nice rich brown colour, the bike runs faultlessly and goes very well and one very happy customer.........
BTW - the bike is on standard air box (snorkel removed, hence bigger jets) and standard exhausts, only other mod is some 6mm reed block spacers and fibre reed petals.......bloody good power for one of them I must say !
So there you go, a combination of main jet, air screw adjustments and needle position all affect things in various ways, its not as easy as some would have you believe
HTH
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rebore
Aug 28, 2013 17:48:36 GMT 1
Post by muttsnuts on Aug 28, 2013 17:48:36 GMT 1
Should be fine standard, suspect its got an air leak somewhere. Mine has the weak stutter you speak off bit only when its cold, a quick touch of choke is all that's needed to cure. No issues when warm when the mixture is then correct. true, that would do it, check your carb/reed block rubbers for small cracks etc, seen a good few that have been split, a set of new ones have transformed a few bikes that I've had in with this issue
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rebore
Aug 28, 2013 17:49:21 GMT 1
Post by thehut on Aug 28, 2013 17:49:21 GMT 1
lifting the needle makes it worse. i tryed that also thaught if you screw air screw out that makes it weaker. in richens it up i thaught. what about the reed valve stops. mine are wider than they should be. never thaught trying the choke to see what it does
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rebore
Aug 28, 2013 17:57:38 GMT 1
Post by thehut on Aug 28, 2013 17:57:38 GMT 1
iv tryed spraying easy start over all the joints. and rubbers but nothing seems to hapn so. it dont seem to have a leak. can you confirm screwing air screw in richens mixture up. if not im going wrong way. might have to take it to jack armstrongs at newcastle. if i cant sort it
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rebore
Aug 28, 2013 19:30:27 GMT 1
via mobile
Post by davey on Aug 28, 2013 19:30:27 GMT 1
Opening the air correction sctew alows more air in so hence a leaner mixture, closing or screwing it in cuts back on the ammont of air making ot richer.
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rebore
Aug 28, 2013 20:14:52 GMT 1
Post by thehut on Aug 28, 2013 20:14:52 GMT 1
cheers thaught i was right. says in manual if throttle valve is worn this can cause leeks. one of mine has a score mark down it
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rebore
Aug 28, 2013 21:36:27 GMT 1
Post by muttsnuts on Aug 28, 2013 21:36:27 GMT 1
umm, what carbs are on it, need the exact numbers, so are they 4L0 00 or 4L0 01 or something else?
once you post the number we will be able to give you a stock set up/configuration to check against
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rebore
Aug 29, 2013 0:21:32 GMT 1
Post by thehut on Aug 29, 2013 0:21:32 GMT 1
ok ill post numbers in morning. i know there the later carbs. cant remember what number stamped on them.
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rebore
Aug 29, 2013 10:52:45 GMT 1
Post by jollyjoiner on Aug 29, 2013 10:52:45 GMT 1
I had to drop my needles in mine to make it cleaner mid rev range, mine was bogging bad as it was getting to much fuel, seems ok now
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rebore
Aug 29, 2013 11:03:36 GMT 1
Post by thehut on Aug 29, 2013 11:03:36 GMT 1
umm, what carbs are on it, need the exact numbers, so are they 4L0 00 or 4L0 01 or something else? once you post the number we will be able to give you a stock set up/configuration to check against hi there my carb numbers are 4l0 o1 v2 cheers
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rebore
Aug 29, 2013 12:12:51 GMT 1
Post by muttsnuts on Aug 29, 2013 12:12:51 GMT 1
ok great, in which case if memory serves me right, the base settings are;
220 mains 22.5 pilots 5k1 jet needle with clip set at mid position (3 from top) P-2 (345) needle jet (emulsion tube) 1.5 turns out on air screw 21mm float height
HTH
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rebore
Aug 29, 2013 12:37:03 GMT 1
Post by thehut on Aug 29, 2013 12:37:03 GMT 1
ok great, in which case if memory serves me right, the base settings are; 220 mains 22.5 pilots 5k1 jet needle with clip set at mid position (3 from top) P-2 (345) needle jet (emulsion tube) 1.5 turns out on air screw 21mm float height HTH everything ok in that department then. i might try lifting needles again 1 notch. as i only done the side that was weak before. but it made misfire worse. cheers
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rebore
Aug 29, 2013 16:56:20 GMT 1
Post by thehut on Aug 29, 2013 16:56:20 GMT 1
ok great, in which case if memory serves me right, the base settings are; 220 mains 22.5 pilots 5k1 jet needle with clip set at mid position (3 from top) P-2 (345) needle jet (emulsion tube) 1.5 turns out on air screw 21mm float height HTH this is best i can get plugs. been on most of day. needles lifted 1 notch. air screws now 1 turn out. so got me beat unless i need to go up on jet size from standard. bike still holds back and has misfire. noticed iv got a lot of oil over numberplate and back of bike out exhausts.
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rebore
Aug 29, 2013 17:10:57 GMT 1
Post by muttsnuts on Aug 29, 2013 17:10:57 GMT 1
um, hard to say, whereabouts are you, could be the air correction jets are blocked, have the carbs been vapour blasted per chance?
also, have you checked that the carbs are balanced, e.g, have you taken the blanking plugs out and checked that the slides are rising at the same rate up to full throttle, have you got a Yambits throttle cable fitted as well, if so, I'd be checking the slide synchronisation as I've had a few issues with their cables and all have been that problem
HTH
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rebore
Aug 29, 2013 18:03:32 GMT 1
Post by thehut on Aug 29, 2013 18:03:32 GMT 1
um, hard to say, whereabouts are you, could be the air correction jets are blocked, have the carbs been vapour blasted per chance? also, have you checked that the carbs are balanced, e.g, have you taken the blanking plugs out and checked that the slides are rising at the same rate up to full throttle, have you got a Yambits throttle cable fitted as well, if so, I'd be checking the slide synchronisation as I've had a few issues with their cables and all have been that problem HTH iv checked them by the windows. when i had carbs off. i sett both slides the same. but noticed when you opened them full you could only see 1 dot in window. and had to ajust 1 quite a bit so they were right at full throttle. not sure about the cable as i baught it off lad on here that rebuilt it. not sure if he had them vapour blasted or not. but seen on one of his threads on here he was told to use cilit bang to clean them. only thing thats got me puzzeld is all the brass blanking balls seem to have green round them. as if they have been locktighted in. can you get in to the air correction jets to clean them. iv got chance of a good sett of 250lc carbs if its possable to use them. i live at newcastle tyne wear
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rebore
Aug 30, 2013 9:38:35 GMT 1
Post by muttsnuts on Aug 30, 2013 9:38:35 GMT 1
Hi, the air correction jets are behind the biggest brass ball, only way to clean them properly is to remove the brass ball and then replace it. Never used cilit bang to clean out - I use an ultrasonic cleaner and good old elbow grease !
The pips on the slides do need to align and rise and fall at the same time, sounds like you have done that check, so we can rule that out, it does sound like the air correction jets could be blocked, but to be honest there are a whole load of possible things it could be.
I am in North Yorks (YO17 9DS) so not a million miles away from you, I do have a spare set of carbs that I could loan you to check if it is your carbs or not, these have been fully stripped and set up by me, so I know they are good and are my set that I use for diagnosing faults etc, and eliminating carbs on bikes that aren't running right.
Your welcome to either bring your bike down and try them or I could post them up to you if you cover the costs and promise to get them back to me pretty quick as I do use them a lot
Let me know
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rebore
Aug 30, 2013 10:04:02 GMT 1
Post by seahorse83 on Aug 30, 2013 10:04:02 GMT 1
While you have the carbs off Id be checking the reeds. PS less than 1/2 a turn out on the airscrew com up a pilot size, more than two turns out come down a pilot size. Its sounds like you need to get the manual out and start from scratch. Fist make sure emulsion tubes, pilots and mains are clean. Set float heights,then throttle stops,then balance, in that order. Double check your cables are seated properly before you balance. If its a YPVS by the sounds of your needle it is, you can balance the carbs by removing the top half of the airbox and looking at the slides come off the bottom at exactly the same time. Make sure when you clean your carbs you do not mix your float bowl's up. Choke enrichener hole float goes on choke "left side". And double check your vac line is connected to the right place on the right carb if you haveone.
Id still be checking the reeds, when you have the carbs off.
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rebore
Aug 30, 2013 10:50:12 GMT 1
Post by thehut on Aug 30, 2013 10:50:12 GMT 1
Hi, the air correction jets are behind the biggest brass ball, only way to clean them properly is to remove the brass ball and then replace it. Never used cilit bang to clean out - I use an ultrasonic cleaner and good old elbow grease ! The pips on the slides do need to align and rise and fall at the same time, sounds like you have done that check, so we can rule that out, it does sound like the air correction jets could be blocked, but to be honest there are a whole load of possible things it could be. I am in North Yorks (YO17 9DS) so not a million miles away from you, I do have a spare set of carbs that I could loan you to check if it is your carbs or not, these have been fully stripped and set up by me, so I know they are good and are my set that I use for diagnosing faults etc, and eliminating carbs on bikes that aren't running right. Your welcome to either bring your bike down and try them or I could post them up to you if you cover the costs and promise to get them back to me pretty quick as I do use them a lot Let me know hi there thanks for the offer. can i check if the air jet is blocked without drilling the brass ball out. ill have bit mess on today. was thinking could i send my carbs to you. to see if it is them. that way you not without your carbs. and i would pay you for work you have to do on them
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rebore
Aug 30, 2013 12:11:54 GMT 1
Post by thehut on Aug 30, 2013 12:11:54 GMT 1
While you have the carbs off Id be checking the reeds. PS less than 1/2 a turn out on the airscrew com up a pilot size, more than two turns out come down a pilot size. Its sounds like you need to get the manual out and start from scratch. Fist make sure emulsion tubes, pilots and mains are clean. Set float heights,then throttle stops,then balance, in that order. Double check your cables are seated properly before you balance. If its a YPVS by the sounds of your needle it is, you can balance the carbs by removing the top half of the airbox and looking at the slides come off the bottom at exactly the same time. Make sure when you clean your carbs you do not mix your float bowl's up. Choke enrichener hole float goes on choke "left side". And double check your vac line is connected to the right place on the right carb if you haveone. Id still be checking the reeds, when you have the carbs off. hi there reeds have been checkt. and bowls are correct. the bike is rd350lv not the ypvs. going to have another go today if i cant sort it. ill send my carbs off to be checked over
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rebore
Aug 30, 2013 19:15:52 GMT 1
Post by seahorse83 on Aug 30, 2013 19:15:52 GMT 1
Roger mate, re read its a 4lO. I dont think you will go far wrong with the factory settings. Probably start at about 3/4 out on the airscrew, needle middle clip, and jets 22.5 pilot and 220 main, like previously mentioned by mutts nuts and see what happens. If you get the carb all clean and set right to factory settings and still rins rough, id be looking elswhere, cracked crossover tube, leads, plugs,fuel cap vent etc.
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rebore
Aug 30, 2013 20:04:56 GMT 1
Post by thehut on Aug 30, 2013 20:04:56 GMT 1
Roger mate, re read its a 4lO. I dont think you will go far wrong with the factory settings. Probably start at about 3/4 out on the airscrew, needle middle clip, and jets 22.5 pilot and 220 main, like previously mentioned by mutts nuts and see what happens. If you get the carb all clean and set right to factory settings and still rins rough, id be looking elswhere, cracked crossover tube, leads, plugs,fuel cap vent etc. iv checked most things now. and it still no good if you get it in top gear it seems to be misfiring right up the rev range all the time. iv just changed coil as the other lad had put one on that was not standard. i think it has slight improvment now only slight tho
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rebore
Aug 30, 2013 20:08:58 GMT 1
Post by arrow on Aug 30, 2013 20:08:58 GMT 1
Try a different stator if you can get your hands on one.
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rebore
Aug 30, 2013 20:49:19 GMT 1
Post by thehut on Aug 30, 2013 20:49:19 GMT 1
Try a different stator if you can get your hands on one. it got a new stator on. the lad i baught it off put it on. thaught the stator was for the charging on it. only thing about the new stator. he said when it came it did not have plug on it to match loom. so he put the pins directly in loom. i foned them today. and they said they send them back. the way you send them to be rewound. its the plug with the 3 white wires and a blue one. not sure if it maters what way round the 3 white ones go
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rebore
Aug 30, 2013 20:59:50 GMT 1
Post by muttsnuts on Aug 30, 2013 20:59:50 GMT 1
you got a van?, if so, bring it down to me and I'll find out what's wrong with it for you, Cuzza off here had a problem with his and he brought it down and I got it sorted for him. I have all of the parts and tools necessary to diagnose what it is and check everything regardless of what has been done previously. if its the stator I have one I use for diagnosing etc, as I've said previously it could be a number of things unfortunately and remote diagnosis is quiet a hard thing to do really.
your not burning oil on the right hand pipe (as sat on it) more than the left are you?, if so it could be a crank seal. Have you checked the crank seals while we are on the subject ?
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rebore
Aug 30, 2013 23:59:11 GMT 1
Post by thehut on Aug 30, 2013 23:59:11 GMT 1
you got a van?, if so, bring it down to me and I'll find out what's wrong with it for you, Cuzza off here had a problem with his and he brought it down and I got it sorted for him. I have all of the parts and tools necessary to diagnose what it is and check everything regardless of what has been done previously. if its the stator I have one I use for diagnosing etc, as I've said previously it could be a number of things unfortunately and remote diagnosis is quiet a hard thing to do really. your not burning oil on the right hand pipe (as sat on it) more than the left are you?, if so it could be a crank seal. Have you checked the crank seals while we are on the subject ?
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rebore
Aug 31, 2013 0:02:34 GMT 1
Post by thehut on Aug 31, 2013 0:02:34 GMT 1
hi there no its the left exhaust thats got more oil than the right. i could get van from work if i need to. just waiting to find out if the lad had the carbs ultrasonic cleaned. as im going to get them done if he did not. so ill get back to you
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rebore
Aug 31, 2013 19:44:06 GMT 1
Post by thehut on Aug 31, 2013 19:44:06 GMT 1
hi there no its the left exhaust thats got more oil than the right. i could get van from work if i need to. just waiting to find out if the lad had the carbs ultrasonic cleaned. as im going to get them done if he did not. so ill get back to you
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