Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: Itsme on January 26, 2024, 05:24:11 PM
-
Thanks to all of you gents who have been so generous with your advice and encouragement, not to mention patience, I had another go at cleaning the carb on the MM today and with the help of a little WD40 as a starting fluid it chimed into life! What a fabulous moment. There is a lot of fettling and tidying to do but now I have the enthusiasm back.
Thanks once again all, I think without your help the MM might just have been consigned to a dark place.
Ian
-
Ace news…..I’ve been following your struggles Ian. Top work.
-
Ace news…..Top work.
The first two words of Kevin’s post say it all Ian. Proper chuffed for you, perfect timing too (see what I did there 🧥🚪🚕🤦???) nicely give you time to get all the other bits n bobs sorted ready for the clocks going forward and those lovey warmer days sneaking in. Great stuff... the MM rides again 👍
Cheers, Michael
-
Thanks chaps. I am looking forward to many more miles on the little beggar when I have finished fettling.
Ian
-
Bit of a false dawn by the looks of things, though bad and good. I tried the MM this morning and no go unless I used starter fluid (WD40) so at least now I can be confident that it is a fuel fault. When I can be bothered I will buy a cheap Chinese carb and also refresh the fuel in the tank which being E10 is rumoured to lose its volatility quickly and the stuff in the tank is now a couple of months old.
One step backward but another forward. Remind me, why do we like old bikes? Just off for a toddle on Newzuki.
Ian
-
Good - if mixed - news Ian. I've fitted a Mikuni clone to the Tri-Greeves but it isn't entirely successful partly because I had to severely butcher the flange to get it to fit. However it was only £15 or so and seems very well made. I doi have a selection of slow running and main jets if you go down that route.
I've rebuilt the original monobloc but haven't been able to try it yet.
-
Aye Ian,
E10 older than 6 weeks, without fuel stabiliser, is p!sh! Throw it away and get some fresh E5 in there, with stabiliser, afore spending more filthy lucre on a Chinese carb. Pleased to note that the wee whizz bang hasn't coughed it's last. ;)
Good health, Bill
-
Yes got to be E5 defo. I never put E10 in either of my bikes (900 speed twin & 125 grom) even tho they are both new. Do as Bill suggests Ian and try some new fuel in first 🤞🤞
Cheers, Michael
-
Thanks gentlemen, as ever a mine of useful information. It is good to know Ian that a cheap Chinese carb wouldn't be a complete waste of money, but taking the advice of Michael and Bill I will be trying some fresh E5 first.
I am sure the MM wants to run, now more so than ever, but like our long-case clock once one tiny thing is disturbed lots of other things seem to go out of adjustment. I am pretty sure that if I get the motor running then I can work through the other things methodically and have the bike ready for spring. With Justin our clock (Justin Time - sorry) we wait for our friend Trev to pop over as he is an horologist and knows what to tweak to get it running again, sadly he knows nothing about thumpers. But you lot do!
Ian
-
Aye Ian,
Thank you for your generous compliment.
As for longcases, worth diddly squit these days, I have a bitsa, assembled by my Great grandfather that my Dad gotn running again. However, since Dad's passing I haven't re-assembled it, as we don't have a permanent space for it. You may have poked the nerve! ;) It has a nice mechanism, but the old oak case was "relief carved" by some Victorian butcher, as was their want at the time. :(
Good health, Bill
-
How right you are Bill, longcases can be picked up for a few quid now. We didn't pay a lot for Justin as he is a marriage of movement in a different case. We bought him about 15 years ago and only keep him so Trev has something to do when he comes down from Yorkshire, without his free ministrations Justin would have been 'beyond economical repair' long ago.
We also had a bracket clock given to my wife by her friend when her husband died as Hilary liked the clock. Jules her friend had had the clock 'repaired' in Egypt where she has lived for the past 40 years and when Trev looked inside it he just made horrified noises and muttered 'there's an effing nail in here holding the mechanism in'. I don't think he was impressed.
Ian
-
Just a quick update. I have now simplified and renewed the wiring and have a much stronger and more consistent spark which is obviously good. However at some point over the next few days I will be draining the carb and trying a start on lovely, fresh E5. If the MM runs then all well and good, if not then I am at a loss.
Fingers crossed and I will let you know the results.
Ian
-
Certainly sounds promising Ian, hopefully that bit of light at the end of the tunnel for you with it all now. Best of luck with it and keep us posted on your progress. The MM WILL ride again 😉🤞
Cheers, Michael
-
As the above Ian. Good luck.
-
Fingers crossed Ian...
-
Hi All
Well I have had the MM running on petrol. But not with any great consistency, sometimes it will start and sometimes not. Either way whenever it did start there was no tickover. I have tried everything that you have suggested and everything I know but the result is that I am no nearer a solution than I was months ago.
I have the Inazuma which I am happy with so rather than spend any more time or cash on the MM just now it is going under a cover until inspiration or enthusiasm strike me again.
Thanks for all the help but time to move on.
Ian
-
Today.... is a sad day
Today... the MM has been put under a cover in the corner of a dark n gloomy garage (when Ian turns the lights off anyway) possibly never to see a stretch of tarmacadam again 🤷???
At least you gave it your best shot Ian!! Who knows you may just come to enjoy the inazuma given a bit of time and hopefully some sunny ride outs in the not to distant future 🤞🤞
Cheers, Michael
-
Thanks everyone. Michael you have a talent for sympathising and yet inspiring me to keep looking for possibilities. The MM is currently 'resting' but fear not I already know that I just can't totally abandon the little brute. I shall take a break and enjoy Newzuki the Inazuma for a while but I will re-visit the MM soon.
Ian
-
Hello all
J thought a quick update and a question were in order so here is the latest on the Mighty Midget.
After, using fresh fuel and fitting a Chinese carb specified for a GN250 I can now more-or-less get a consistent start, even though there is some 'chugging' to get a start if I have left it for a few days. If I get the motor warm it will happily tick over and stay running for as long as I want. BUT there is a huge flat-spot just off idle that will bog the motor down and cut it out and although once properly warm it is possible with a little throttle juggling to get the engine past the flat-spot so that it revs high with no problem. I have checked the float height and it is fine.
To me this would seem to indicate that the needle is too rich, but what do you think?
I'd be grateful of thoughts as I just don't want to leave the MM when I am so close to getting it back to full health. At the moment i am taking a wee break from the bike as a) I have the Inazuma and b) it is my wife's birthday on Friday and I have a small metal work project to finish for her as a present.
Grateful for any advice as ever chaps.
Ian
-
If it's just off idle then it's usually the cutaway at fault (too weak ie higher number) as the needle - in theory - doesn't start to take effect till the throttle is opened further. I tried a Chinese carb on my Tri-Greeves and it worked quite well but had to bodge it around a bit.
It might be worth trying a richer idle jet. I have a small selection (for Mikuni VM22) as well as some main jets if they would help - no further use for them.
-
Hi Ian
Thanks for the info and the offer of jets (another thoroughly nice TC chap is Ian). I am having a break from the MM, but when I get back to it I will let you know if I need anything.
Thanks
Ian
-
Hello All
After exhausting my tiny brain with possible faults I finally got round to buying a compression tester and I think I really have found the problem now. The tester read a high of 75psi which as far as I know is way too low. So it will be an engine out job when I have time and a look for a stuck valve, debris under a valve or even the demise of my cheap Chinese piston rings which have done about 3000 miles.
Anyway it is a job I will get round to eventually, but at least I have a definite idea now of what I'm looking for.
Ian
-
Right this time I really have found the problem! After finding the compression to be so low I decided to strip the top end of the Mighty Midget's motor and have found that one of the exhaust valves (four valve head) has a piece missing! A small piece has broken off from the edge of the valve, there is evidence of some minor dimpling on the front of the combustion chamber where the piece must have hammered around a bit before exiting out of the port. I haven't stripped the valves out yet, but I expect the seat is damaged as well.
When I rebuilt the top end last year I noticed that the valves were looking a bit tired so don't think anything too nasty has happened, I think they were just worn out after 30 years and 51,000 miles. The rocker arm contact pads are very worn as well though the cam is still in excellent condition as it runs in an oil bath.
I know a small, local engineering place run by a chap who is into his older bikes so I will pop in to have a word with him about the cost of a head re-build. It might cost a bit, but as I said to my wife it will be cheaper than buying a new bike and I really do love the MM so it would be worth it.
Ian
-
Sounds good Ian. If one exhaust valve has failed it may be a good idea to change both?
-
Thanks Ian, I still haven't decided what to do with the MM, but I have found a complete set of second-hand valves on ebay for about £25 so if the valve seat on the broken valve has survived I might just buy them and renew all of the valves. Obviously it will depend on me being able to lap the new valves in if the seats are ok.
This would be one way of getting the MM back on the road as cheaply as possible, but it might not be the right course of action in the long run. There are lots of little niggles that really need addressing and now, whilst the bike is apart seems to be an opportune time to do them. There will be a cost implication, but as I said in my previous post any outlay will be far less than if I were to buy a new bike to replace the wee beastie. Besides which I am really getting into the Inazuma, it is quick enough, handles well now I have it sorted and is very reliable and easy to run. No it doesn't have the 'character' of the MM or bikes like it, but maybe just for once I could be tempted by a summer of trouble-free getting to places and enjoying riding. Long-term it will have to go as it still upsets my knackered shoulder, but hey ho why not make hay whilst the sun shines!
Ian
-
Just a quick update. I looked again at the valves on ebay and they're not worth buying. The exhaust valves have been ground flat on the faces and three of them seem to have two collet grooves rather than the correct one.
The search goes on.
Ian