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‘AAA Dummy
Membertry ost2rad.com
‘AAA Dummy
MemberThanks Derek. Its so easy to get confused over the terminology. In the Mikuni case I think I’m right in saying it is a fuel metering screw. So when it is screwed right in it should shut the fuel off which is now the case but it keeps running so is getting fuel by another route right. The carb came with spare, different sized spare jets. Time to try one. Bigger or smaller. Will be a pure guess on my part. My old brain can’t handle the logic approach.
I vill be back !‘AAA Dummy
MemberForesure – Let us know. Almost in the same boat myself. As mentioned fitted a new Mikuni to my Sup5. It does start – eventually (I was hoping for first kick) and as you say the plug never gets wet. I have even tilted the carb over to favour the level in the enrichment chamber, might have helped a bit. Now a a questo of my own, tinkering with the air/fuel screw yesterday afternoon. It was set about 1-1/2 turns out, I found that it started running smoother and happier with it screwed home, right in !!! What does that mean oh wise ones. Remember its a Mikuni.
‘AAA Dummy
MemberDone all that Darren and more. You have my sympathies. Even fitted a new Mikunu. It fired up third kick – Hurrah but not since, not never.
Tell me does your plug ever get wetted with petrol, mine is always bone dry.‘AAA Dummy
MemberWell yes, ONLY 50,000 miles… My question was mainly pertaining to MZ’s on original Carbs.
I myself am coming up to 90k miles on my own CX500, Derek. Despite the other faults, fuelling has never really been a problem there… The slides are still pretty much perfect- infact I’ve never done any repair work on those carburettors..
Of course- it could simply be the metalurgy at that period of time in that particular location WRT the british made carbs and the BVFs. Singles could still have something to do with it though(?) as although a multicylinder has a carb per cylinder, they do not typically exert the vibration that a single does- esspecially with the MZ’s and the excessive movement allowed by using soft engine connections (would it help, or exacerbate). The only thing I could relatively do without much more invasive and perhaps machining work, would be simply to find a low mileage slide as the cheapest option first.
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This reply was modified 3 years, 11 months ago by
'AAA Dummy.
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This reply was modified 3 years, 11 months ago by
'AAA Dummy.
‘AAA Dummy
MemberBeen there, done that Brian.
As a commutor bike, this sort of problem bugs the hell out of me so I did indeed put the 30n2.5 from my etz250 onto the bike in question and well.. it was perfect. Reved cleanly and smoothly and it was great.
The ultimate test would be to put the 30n3 onto the etz250 and see if that also gets 3-4k stutter. But it’s fairly conclusive.
I would like to try a replacement original 30n3 carburettor slide before , if anyone has one spare they would like to sell before I blame the carburettor inner bore perhaps…
I know a lot of people blame wear on carburettors, but who else has a genuinely well working original carburettor with 50,0000 miles on it? It seems odd, because there is scoring on the slide sure, but it’s not too bad- and it doesn’t exert much play.
‘AAA Dummy
MemberThanks Peter, good to get the feedback.
A piece of detective work and as you say, something to pass the current
excess of time.
Regards Rob.‘AAA Dummy
MemberHi guys,
Have changed coil for a known working one- no difference.
The bike in general does feel much peppier but only since cleaning out the carb thoroughly. It does feel a lot better, but don’t get me wrong, the bike only does the ‘stutter’ when the throttle is at a steady position and the rpm is going up on the engine in a gradual and civilised way (until anywhere between 3-4k) when it will require either a gear change, or more throttle to circumvent this. Most prevelent when cold, but it’s a lot better now that I cleared out the carb. If I am actually trying to get somewhere fast, then you don’t really even notice it- and of course- i’m tainted and biased now though – my senses are in tune now to find any fault in that range.
I’ve been looking at the slide, and although there is very little play slide in bore, there is significant scoring, piston side. It’s had these since I know, but of course with an extra 17k on it in my ownership wear will always occur.
I’ll be looking to find a low mileage original slide first, because I hate mucking around with bikes that are working perfectly, – but if I cannot then I will definitely be taking that other carb.
New spark plug cap and HT lead were installed only a few months ago- I can check the resistence in the cap- but normally when caps have resistors with high resistence it mainly causes a lumpy idle- but it’s a perfectly valid thought. I’ll check it.
I use Denso W22FSU sparkies, and i’ve already tried a handful, including of different makes; champion, ngk, beru- but no effect.
‘AAA Dummy
MemberHi both,
Thanks for the replies.
These sorts of problems can make you go down the wrong rabbit hole.. I do have a spare coil, which might be easier for me to just swap over as my first thing to do.
If it still feels odd, and no change then I’ll nick the 30n2.5 from my etz250 and see what that does.
As for the exhaust, i’ve already cleaned it out thoroughly about 3k miles ago- and a little bit of crap did come out. I know that the exhaust block can cause the problems I have, because my Suzuki TS185 also has the same symptoms- although the difference there is that the symptoms are worse when cold, and then start to gradually go after the engine has been running for an hour or two and everything is nice and hot and you’ve blasted it a little bit…
Coincidentally, I’ve already swapped exhaust with the 251 trying to find another problem with a different bike (actually a restrictive exhaust), and the 251 felt no difference with a known recent and nicely flowing exhaust..
Will keep this updated.
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This reply was modified 4 years ago by
'AAA Dummy.
‘AAA Dummy
MemberAs stated earlier I had a similar prob with my cb77 twin. All fine till it got into the higher rev range, particularly on the motorway. Like you, I was convinced it was the mixture. Played with the jetting for about a year even though I had bought new coils just in case. Wanted to keep it standard like but when I did remove the coils I found the problem side had leaked its oil into an almost solid goo. Sorted !
So try another coil, not expensive.‘AAA Dummy
Member🙂 Look Brian, I’m the one whose avin a larf, avin a larf, avin a larf.
‘AAA Dummy
MemberThanks, all interesting stuff guys. Did look to lower my footrests but gave up, so how did you arrange yours Peter.
Have been having great probs with motivation but the article on the 502 really perked me up. Really good piece specially at the end when the cockups are admitted. I make plenty. 🙂-
This reply was modified 4 years ago by
'AAA Dummy.
‘AAA Dummy
MemberThank you guys for your replies , having asked around the trade I am going with the center of the pin. My problem is that not all suppliers quote the crown height and the ones that do don’t say where they take the measurement from. Some will just ask
what machine is it for, In my case this is no good as I am looking for a pair of pistons to fit an Adler MB250 twin that I am rebuilding, It will have Kawasaki KX125 motocross conn rods. All good fun While in lockdown.
Regard John‘AAA Dummy
MemberInteresting Mr Bond. I haven’t the heart to tell Burlens – yet.
Cheers.‘AAA Dummy
MemberHi, well the Mikuni is fitted (yesterday) And she fired up on the ninth kick which to me was incredible. Fitted but not sorted out the intake hose yet so seems a bit weak low down but of course as said it came with spare jets so can change if necessary. Did a slight miss service to Motocarb, the price actually was £165.00 + del. Do like the feel of it. For your interest the enrichment chamber is at the engine end of the body so must make it more responsive.
Skimmed a few thou. of each end dia. (see pic) to give a good fit in the manifold.
Still have to sort out the inlet hose. Would you believe it had split just sitting there. Twas only eight month old. Old stock do you think ? Trying Supaglue, well they are over thirty quid now. Did half try your suggestion of paring the hose out to suit the flange dia Ian but wasn’t happy with the way it was going. Still pondering on’t.
Below should be a pic of it in the lathe. Used a boring tool so as to miss the choke lever.
Hasta la Vista Amigos.-
This reply was modified 4 years, 2 months ago by
'AAA Dummy.
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This reply was modified 3 years, 11 months ago by
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