Dear all,
I am in the process of repairing the broken kick on my C15. I am at the stage of refitting the inner side cover.
I thought I would trial fit the cover before fitting the gasket and sealant and I am glad that I did.
Is the a clever trick to get everything to line up properly? I put the cover on and started tightening up the bolts but he cover wouldn't lay flat.
It looks like the slide rod which the selectors slide on isn't popping neatly into its hole. Is there a trick to doing this?
Regards,
Ian
OK.
I managed to get the side cover on after a couple of attempts.
I am feeling five gear positions. I am guessing that neutral is at the bottom between 1st and second. That is what it feels like. However the back wheel won't turn at this point. I think I need to open it up again and take another look . Any ideas much appreciated of course.
Also the clutch not operating but that is another story.
Time for a break I think before I open it all up again.
Regards,
Ian
If you are getting 5 gear positions, it would imply that the selector forks at least must be moving correctly otherwise they would jam. Can you use the kickstarter shaft to see whether this rotates the gearbox to check the gear shafts didn't lock up when you tightened down the inner timing cover?
Yep. I took the inner cover of the engine again this morning and as the cover started to work loose I could feel the gears start to turn, so it seems that the bush was pushing the gears tight together locking them.
I watched one of the very useful youtube videos to check that I had the bush the right way around with the head on the inside, and it is. To be honest you can't put the head on the outside because it would not be possible then the fit The little internal clutch lever.
Measuring very inaccurately with my vernier calipers the new bush sticks out by around 3.5mm vs 2mm on the old (and very worn) one.
So it looks very much like I will be filing a mm off of the new bush. Of course I will mask up the mating surfaces of the plate to prevent accidental gouge marks from the file. I expect I will be looking to do that next weekend, so plenty of time for helpful suggestions via this forum in the meantime.
Interestingly there is a tiny steel pin inserted into the alluminium casting alongside the brass bush which appears to be there to lock the bush. It didn't work on the old bush and acted like a lathe tool chamfering the edge off when the bush spun.
Normally, when you put a gearbox back together with new bearings, whether they be bushes or ball races, you have to accurately measure the free play on all the shafts and then shim where necessary to bring the free play into spec.
In this case, it is possible that the old bush is now quite worn and may have started life at 2.5 mm or even 3 mm. Without accurately measuring the current free play, it will be difficult to work out how much of the bush to remove. The aim should be to leave a free play of the order of 10 thou.
I would definitely not recommend taking a file to the bush but, if you can work out how much of the bush flange needs to machined off, I would be happy to do it for you on my lathe.
Very kind of you spaceman, thanks.
So, going by your message, are there shims which I can take out? Not something I have noticed.
Before machining the bush,I will need to remove it from the cover (how annoying! ) Luckily we have a machine shop at work. I will see if they can make me up a simple drifting tool. That would save the ring marks on the end of the bush which I got as a result of using a deep socket. And then, of course, they can skim the end of the bush too, so, hopefully I won't need to take advantage of your kind offer.
I am definitely putting a small lathe on my wish list.
Ian
my B40 cover was binding, only found on assembly, a thread on here somewhere.
I took the middle part off and put up on my small lathe bed, as it has the drill/mill head attachment, I managed to put a small 8 or 10mm end mill up and using the cross side in two directions, managed to skim 0.008 thou off without having to remove any shafts and gears. covered them with a polythene bag.
if you have access to a machine shop, it should be an easy job, I couldnt wait to take in to work but the Clarke lathe/mill managed fine.
I've got a similar issue with a D7 Bantam engine. When I do the cases up tight the gears lock solid. There are two bushes for the layshaft, should I be looking to take a little off both of them or can it all come off one?
TIA
If you only replace one D7 bush then that would be the one to skim. If you replaced both, it would probably be safer to skim each bush equally although, in a 3-speed Bantam gearbox, I doubt if it would make much difference if you skimmed just one!
I watched Michael Waller's video on Youtube ( https://www.youtube.com/watch?v=6pvxNlggxOk )
After wading through a lot of irrelevent stuff I watched him put the cover on and BINGO, he had exactly the same problem as me. It turned out that the kickstart stub shaft was in slightly the wrong position. With the shaft aligned as it would be in operation everything popped together neatly and the engine turned over fine.
Thank you Michael!!
BTW another question.
Not knowing any better, when I put in the new bush, I pushed in the bush on top of the steel retaining pin on the assumption that the sharp end would grip the bush.
Now looking at the broken remains of the original, it looks like maybe the bush was drilled through and the pin inserted afterwards. Is this a problem? Should I drift out the bush and the pin and re-do?
Thanks,
Ian
OK Looking closer it appears that the pin was inserted first before the bush, so that the end surface is just brass, to rub against the steel of the gear next to it, so I think what I have done is correct. Before I put it back together, I am assumng that the C15 is a wasted spark engine? i.e. It sparks at the start of both the power and exhaust strokes. There are marks on both of the two timing gears to line up, but one gear is twice the size of the other. I was worried that I might put the big gear in 180 degrees out leading to an issue.
Quote from: Barnsey on 06 Mar, 2022, 17:41
BTW another question.
Not knowing any better, when I put in the new bush, I pushed in the bush on top of the steel retaining pin on the assumption that the sharp end would grip the bush.
Now looking at the broken remains of the original, it looks like maybe the bush was drilled through and the pin inserted afterwards. Is this a problem? Should I drift out the bush and the pin and re-do?
Thanks,
Ian
Yes. I would drill a slightly oversized hole in the bush to give you a bit more tolerance when putting it all back together - the pin does not need to be a tight fit in the bush - it's there just to stop teh bush from rotating!
Quote from: Barnsey on 11 Mar, 2022, 13:55
OK Looking closer it appears that the pin was inserted first before the bush, so that the end surface is just brass, to rub against the steel of the gear next to it, so I think what I have done is correct. Before I put it back together, I am assumng that the C15 is a wasted spark engine? i.e. It sparks at the start of both the power and exhaust strokes. There are marks on both of the two timing gears to line up, but one gear is twice the size of the other. I was worried that I might put the big gear in 180 degrees out leading to an issue.
The camshaft and contact breaker cam rotate at half the engine speed and therefore generate a spark only on the compression stroke. If you line up the timing marks, everything will be fine :)
Thank you for that Spaceman.
I'm in the process of fitting the inner cover with just a bead of sealant, no paper gasket. I will put that somewhere safe for another day.
Most of the bolts I am torquing to a modest 10 foot lbs as per the manual. One or two I am stopping slightly short on where I don't feel confident.
I am fed up over the bottom-most. The bolt which was in there had been hack-sawed too short and was the completely the wrong thread leading to stripping. Unfortunately I didn't notice in time and I aggravated it. For the present I will cut a brand new bolt to the correct length, for maximum bite, and apply a bead of thread lock. At some point tho' I may need to do a proper job and drill and tap it.
As always any tips or advice fully appreciated.
I would buy a Helicoil set and repair the thread which is easy to do - having done all this work, the last thing you want is to get an oil leak because you haven't been able to tighten up one of the screws fully!
Hi,
Repairing the thread is definitely the best option but some times even with the correct length screw there can be some unused thread at the bottom of the hole. If you have to correct tap, gently run it down to the bottom of the hole. This will clean the threads really well. You can then determine the depth available and fit a slightly longer than standard screw. Again being careful not to over tighten.
Dave.
Thank you both. Having measured a bolt they look to be 1/4" BSF ?
Is this a good option? https://www.ebay.co.uk/itm/281957227770?epid=28023463283&hash=item41a5f5dcfa:g:b2UAAOSwLVZVwG65
As per suggestion I will also buy a 1/4" tap so I can try cleaning up the original thread first before committing to helicoil.
Regards,
Ian
They are actually 1/4" BSC but have the same tpi as 1/4" BSF and, in an Aluminium casing, the difference is a little academic.
If you have any doubts about the threads, it's best to proof test each one with the inner cover off to see whether it will take the required torque (whatever that is). If a thread fails the test then Helicoiling is the best repair.
OK, I've ordered Taps, and a helicoil kit in BSC. I had bought stainless steel bolts sold as being for a BSA bike, but suspect they were BSF. I wonder if they would grip as well as BSF.?
The only difference between 1/4" BSC and BSF is the thread angle is 60 deg for the former and 55 deg for the latter. In practice, that normally makes very little difference and in most circumstances they can be treated as interchangeable.
In terms of using Helicoils, it's best to practice on something scrap first because, if something goes wrong, the Helicoils can be difficult to extract and re-do. Using the drill provided to drill out the old thread can be challenging because, if you use a hand drill, it has a tendency race into the hole and be difficult to control. Using a pillar drill is probably safer.
The most important part, apart from the drilling, is to make sure that the new thread for the Helicoil is very carefully tapped and to the correct depth. You then have to be very careful how you screw in the Helicoil spring making sure it screws in smoothly without much force being used!
Slightly worrying when you talk of using a pillar drill,as the engine is in the bike. I wasn't planning to completely strip it down in order to do this job.
I had considered using a hand drill, but I might end up using my makita rechargeable as it will run good and slow.
My normal technique is to use several drills of enlarging sizes to avoid the hole ending up being oversize.
Thinking on it I am wondering about using a drill 0.5mm undersize and then finishing with a hand reamer.
Whatever way I go I will certainly practise on the old cover which is now scrap. :)
I didn't mean an old fashioned hand drill but an electric one. The problem you have to be careful with is that the thread in the existing hole will tend to draw the Helicoil provided drill in very quickly which can be hard to control. Using smaller drills first to gently remove the thread will certainly help but the final one must be the one in the Helicoil kit which is of the correct size for the Helicoil tap provided.
Thanks! I expect I'll be doing dry runs next weekend, I'll let you know how it goes.
Ian ;)
OK it has been a couple of weeks but I have made some progress. Tapping out the holes a little deeper and then cutting the bolts to the right measured length did the trick and saved me from having to drill and helicoil. I'll save my shiny new helicoil kit for next time.
Having done up the side cover I am now worrying over whether I should have shimmed the gearbox having changed the layshaft bush. What do you all think? Is this vital or am I OK to take a chance on it?
Regards,
Ian