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Post by looey on Aug 5, 2009 19:27:30 GMT 1
Hi Chaps,
I know it's been covered before but I'm just trying to get a handle of whether my 125LC actually has a fault or not ?.
I've only run it up the road in 1st and 2nd but it's got so little power before 7,000rpm that it only just has enough power to actually get to the power band. I'm talking near on 10 seconds to pull from 3,000rpm to 7,000rpm on full throttle, surely that's not right is it ?.
Back in 83 I had a 12A model that as soon as it was run in was fitted with a small can Allspeed and the needle moved one clip (can't remember which direction now) and I don't remember it being especially flat out of the power band like this one is ?.
It is an import (don't know where from), 1983 10W model, matching numbers and all that and looks to be pretty std other than the Allspeed pipe. I was told by the previous owner that it's recently had a full engine rbuild so will need running in.
As soon as I get the temp guage working (already diagnosed as the sender) I will get it MOT'd so I can ride it properly and see exactly what's what.
Anyone know the best place to get a sender unit ?.
I do remember on the yamaha-rd site someone posting a similar question but saying that in 3rd gear onwards it was ok ?. Obviously don't know if that's that case here cos I haven't had the chance to try yet.
Laters gaters
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Post by Norbo on Aug 6, 2009 22:15:00 GMT 1
It does seem a little odd . But i hold judgement untill you have run it in and given it some stick . The 125's are crap out the band once you swop to any other pipe but standard. so it could just be that . But i will advise you to go down 1 on the front sprocket this will help now and after its run in . Id have a look at the jet size as well to make sure your not over jeted it should be no biger then a 200.
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Post by looey on Aug 7, 2009 7:19:16 GMT 1
Hi Norbo,
Well a couple of days ago I fitted a new std 16/46 C&S set and noticed that it had been previously fitted with 16/43 which wouldn't have helped it eh ?. .
I'm hoping to get it MOT'd today then I'll take it for a proper run and see what's what. I'll also check the main jet as you say.
I'll let you know how I get on.
Cheers
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Post by looey on Aug 7, 2009 20:35:25 GMT 1
Well I have an update. Today it passed its MOT with flying colours, £15 Tax then out I went ;D So, it's not quite as bad as before, maybe the gearing has helped but it's so peaky it's either 70+ in top or 40-50mph. If you just change gear slightly too early for the next gear to get the lower edge of the power band it just slows down and almost gives the feeling that you are actually breaking !. Is that normal ?. There's certainly no lack of power in the power band but I've only flicked into it cos I'm supposed to be running it in. I still have no temp sender, so I've no idea how hot it's running but before I started my ride the coolant level in the expansion tank was on the max and when I got back it was right up under the filller neck so not sure if it might be running a bit hot ?. I'm not gonna run it again until I get the temp guage working. I must be able to get one somewhere ??, can anyone help ?. Another question I has is with the autolube pump. I took the cover off to check the cable adjustment to the manual but the pulley doesn't have the markings the original Yamaha workshop manual says there should be and the pulley is marked 4L1 ??. I know all 250 & 350LC have a 4L1 marked pulley but a Mk1 RD125LC . Sorry for all these queries, ha ha ha Cheers
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Post by mellow on Aug 8, 2009 15:10:28 GMT 1
damn.just scrapped my cavalier
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Post by looey on Aug 8, 2009 15:40:55 GMT 1
Go get it back, I need that sender unit damn.just scrapped my cavalier
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Post by looey on Aug 10, 2009 17:53:51 GMT 1
Well I took my carb apart again cos it's continuoulsy dripping fuel out of the float bowl overflow and checked the jets whilst it's apart. The main jet fitted is a 140 and should be a 155 according to the Yamaha workshop manual and the 12A model should have a 195 ??. Wots all that about ?. I checked the float height (that's spot on) so it must be a worn needle valve, plus the petrol tap lets petrol past even when on the off position so it's impossible to stop it dripping . Any suggestions as to what jet I should put in there and has anyone got one laying around, oh and a needle jet that won't leak ?. The spark plug is running a biscuit brown all over but I'm only running in so not sure what'll happen when I start riding it a lot harder ?. Cheers in advance It does seem a little odd . But i hold judgement untill you have run it in and given it some stick . The 125's are crap out the band once you swop to any other pipe but standard. so it could just be that . But i will advise you to go down 1 on the front sprocket this will help now and after its run in . Id have a look at the jet size as well to make sure your not over jeted it should be no biger then a 200.
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Post by Norbo on Aug 10, 2009 18:25:23 GMT 1
it may be best to look out for a second hant carb mate . I have some new fuel taps they are £11 and £4 post
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Post by twostroker on Aug 10, 2009 18:59:34 GMT 1
it may be best to look out for a second hant carb mate . I have some new fuel taps they are £11 and £4 post 28mm flatslide off a late dt125r,kr1s,tzr250 is what id stick on it,idealy a nice condition one
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Post by mellow on Aug 10, 2009 21:31:24 GMT 1
Cars now in kazikstan........they love them apparently n pay top money at least it wont leak water inside there ;D I THINK its a land rover one that fits but dont hold me to that but if n e 1 finds out for definate plz let me know as the connector is snapped off my 125 one so i need one to
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Post by twostroker on Aug 10, 2009 22:25:45 GMT 1
i know its erevelant but i fitted a old renalut 5 temp sender to my rd125lc and it made the guage show it was running cool all the time even tho it was 3/4 on the guage.
just be carfulll as not just to fin any sender thet just has the same thread as they are different
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Post by looey on Aug 11, 2009 7:39:28 GMT 1
Yeah good point and I was aware of that. I hopefully have a correct one from an RD125LC coming in the post today or tomorrow. I basically e-mailed every bugger on ebay who had engine parts for sale and finally I got a reply from a guy who had one he could sell me. i know its erevelant but i fitted a old renalut 5 temp sender to my rd125lc and it made the guage show it was running cool all the time even tho it was 3/4 on the guage. just be carfulll as not just to fin any sender thet just has the same thread as they are different
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Post by looey on Aug 12, 2009 14:27:00 GMT 1
So, Finally I found a temp sender after much searching and e-mailing everyone on the internet who had engine bits for an RD125LC (£10 posted) and hooorrraaaaaahhhh, I have a working temp gauge. Took it for a 20 mile run and it fluctuates between 1/4 an 1/3 on the gauge which I suppose is about right ?. Seems to like the rad to be filled about 1in from the top and it stays there. If you put any more in and it pushes the extra into the expansion bottle until it's 1in below the neck again. Isn't loosing water and rides non-stop without getting hot so I assume all is well at the mo. Done 90 miles now pretty much all out of the power band on this engine rebuild, so gonna take it up to the 100 then start using the power band progressively more over the next couple of hundred. Never was one for long run-ins and never had any probs as a result
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Post by tomitch on Aug 12, 2009 23:25:00 GMT 1
i fitted a honda cbr15 temp sender the thread is different so i fitted it any way and the cross-threading process also sealed it :s i was told the other day that the 10w carb had a smaller main jet because the air bleed jet is smaller so it needs less fuel to compensate for all the air my mate has a 125lc 10w but its fitted with a nikon pipe off we think another bike and its gutless untill about 10k rpm then the power band hits lol very odd 30mph before the band hits in 1st gear
good luck running in hope you sort the problem
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Post by carlos on Aug 13, 2009 19:10:58 GMT 1
You can buy needle jets new!
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Post by looey on Aug 13, 2009 19:28:02 GMT 1
Needle jets or needle valves ?. I need a new needle valve assy really to stop it overflowing. I bought some a while ago for my X7 without asking how much they would be cos they are tiny little things....... £85 bleedin quid You can buy needle jets new!
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Post by carlos on Aug 13, 2009 19:42:57 GMT 1
The needle which attaches to the float and stops fuel going into the bowl! Can't remember how much it was, but I didn't pay anywhere near that!
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Post by looey on Aug 13, 2009 20:16:03 GMT 1
Yeah that's the needle valve assy. Ok I'll ask my local friendly Yamaha dealer if he can get me one for a resonable price. Did you just get the pointy needle part or whole the assy with the seat that screws into the carb as well ?. Cheers. The needle which attaches to the float and stops fuel going into the bowl! Can't remember how much it was, but I didn't pay anywhere near that!
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Post by carlos on Aug 19, 2009 17:39:34 GMT 1
Yeah that's the needle valve assy. Ok I'll ask my local friendly Yamaha dealer if he can get me one for a resonable price. Did you just get the pointy needle part or whole the assy with the seat that screws into the carb as well ?. Cheers. The needle which attaches to the float and stops fuel going into the bowl! Can't remember how much it was, but I didn't pay anywhere near that! Whole lot mate, brass bit that screws into the carb etc
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Post by looey on Aug 24, 2009 15:04:33 GMT 1
I've treble checked the float height and just fitted a Brand New fuel tap but that leaks slightly when turned off so got to get that off now and sent back. Aaaaaaaaaaaaaaaahhhhhhhhh. At the moment I am turning the tap off about 20 seconds from home to empty the carb and that way it takes several days for the leaky petrol tap to re-fill the float bowl This bike is driving me mad at the moment. The coolant problem isn't the radiator cap so I'm pretty sure not that it's the head gasket, the water pump oil seal is letting coolant into the gearbox and the clutch is slipping now it's fully run in. Apart from that it's perfect
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Post by looey on Aug 26, 2009 7:20:00 GMT 1
probably the coolant loss fault then mate...sort seal out and renew the plates to be sure ...easy way to clean the white shite out of box is flushing oil and do this a few times before you fill with the good oil... glad your sorting it out though... I'm getting there slowly but time to work on it is pretty limited at the mo
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Post by simon998 on Aug 12, 2020 10:24:59 GMT 1
looey did you ever get to the bottom of the power delivery issue? Mine and my dads are both suffering the same. It won’t go past 40mph in 3rd unless you drop back to 2nd and get it up to 7/8k and into the powerband. It’s a nightmare tbh and takes the fun out of riding it. I don’t want to be screaming at 10k rpm everywhere just to get the thing going.
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Post by looey on Aug 13, 2020 12:35:25 GMT 1
Hi,
Well after a good running in and loosening up it was better but seems a characteristic unfortunately, especially with an aftermarket pipe.
One thing I found was it likes a standard airbox, lid on and tight etc., mine had a Pipercross foam element in it
My bike ended up on a 170 main jet (10w carb) and Micron Exhaust and it was fast (for a 125) but no way pulling into the power band after 3rd gear without dropping down a gear. It was basically ok upto 45mph ish not using the power band at all, any faster, then the power band is required lol.
The bottom end is much better with a standard unrestricted pipe (10W), not so good with an Allspeed and worse with a Micron.
Only other option is a MK3 with working YPVS ?. I had a TZR125 2RK after with working power valve, similar power band power but much more low down grunt
Cheers :-)
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Post by museumman on Aug 17, 2020 13:25:50 GMT 1
I've heard a few stories now of people wanting a RD125LC 'again' then being shocked how poor they were outside of the power band. I sold a bike to a guy who swore it had a fault. Another restorer I know took a bike back for a refund for the same reason.
The only option for the nostalgic with rose tinted glasses , is a YPVS bike (or conversion) with the standard pipe. In Japanese cities you would see the DT engine being fitted for people not caring about top end. The thing is when we were kids top end speed was all that seemed to matter I cant use top end where I live, so will eventually gear it down with sprockets and might consider the DT ratios. This is my YPVS 125. I get grief from big 4 stroke scooters if I'm not ready, slipping the clutch and revving it hard
Michael
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Post by simon998 on Aug 24, 2020 13:47:03 GMT 1
That’s the exact symptoms I’m having at the moment. I’m going to try messing about with lower gearing so hopefully it stays up the revs and In the powerband longer.
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