So, I recently acquired my first classic bike - a 1936 Sunbeam Model 8. I've been an avid reader of classic bike mags for many years but was never able to justify buying one, until now. I'm very excited to be the owner of a Sunbeam and am already enjoying challenging my brain to cope with wrong-side rear brake and gear levers. In fact, the wrong side isn't too bad, it's the upside down change that threatens to overwhelm my meagre faculties!
Which brings me on to my challenge. I've only taken the bike for a few short rides to familiarise myself with its basic workings and am getting more proficient at starting it, but I'm struggling with down changes. Up changes generally go smoothly, but I'm generally ending up in false neutrals between fourth and third and third and second. The clutch bites gently and near the end of the release of the lever, but I don't think this is affecting the quality of the gear change.
My question is, do I need to refine my technique to get the most from the notoriously slow Burman box or are there some adjustments I can make to make the down change more reliable?
Thanks in advance. Looking forward to learning so much more about my Sunbeam and engaging with you in the club.
Hello Fellwalker,
that sometimes happen to me from third to second but I suppose it is a matter of internal play. I never worked on the gearbox and before starting I recommend to check the correct amount of lubrication. Is it oil or grease in your case? I don't know what a "slow" box is but I can change pretty quickly.
Cheers, Thomas
Thanks Thomas, I assumed that checking the lubrication in the box would be a good place to start. Is the only way to check the level by removing the steel cover that has two bolts and is situated under the oil tank? My understanding is that it was filled with grease when the bike was restored and, based on the odometer, that would appear to be about 900 miles ago. The Sunbeam manual suggests checking and topping up every 1000 miles so that could be the culprit. I have bought some semi-fluid grease to use as recommended on these forums.
I guess you talk about this cover. Never opened it but it might be the only checking point, indeed. The problem with grease lubrication is the missing indicator like an overflow hole. So, it is not too clear what "topping up" means and how much grease (yes, semi-fluid) one should shoot through the nipples. I tend to give too much and then the glorious mess slowly drains off the kick start and gear change lever bushes and covers the exhaust. But I consider that as vintage appropriate...
Yes, that's the plate I was referring to. So, you fill the gearbox using the nipples? I can see two - one on the top on the right hand cover and one in the centre bottom of the right hand cover. Since they feed into the cover, I had assumed these nipples wouldn't feed grease into the compartment containing the gears but only into the kickstart mechanism. Or have I got that completely wrong?
Yes, through the nipples. I have four nipples as indicated the pic. It was taken after a 1000 miles trip through the Alps showing the wonderful result of over-lubrication. I can't tell if the grease goes into gear compartment but I think so. I mean, I now rode the machine for about 6.000 miles and all was fine. To really find out you need to open the plate, I guess. I would be interested in a short description if you do so.
Cheers, Thomas
Well, if you've ridden 6000 miles, you must be doing something right! I'll take a closer look tomorrow and plan my next actions. Thanks for your help Thomas.
I got a bit diverted with a more urgent problem over the last couple of days when the carb started flooding. I took the float chamber lid off and the float seems to be floating but the needle seems to be sliding out of the 'cigar cutter' clamp that secures it to the top of the float. I reseated it and it was ok for a few hours but seems to be problematic again today. I see that Burlen have float and needle kits so will probably order one of those for a hopefully easy fix.
Back to the gearbox. I bought the Burman manual for the BA gearbox from the National Motorcycle Museum, which didn't give any more useful information about how to lubricate the box. C'est la vie. However, just as I was considering ways to remove the top plate to check the level, I noticed grease oozing from the nipple in the centre of the kickstart pivot, so I assume there must be a decent amount in there. I went for a ride instead and tried a few different down change techniques. What seems to work best is to let the revs die, pull in the clutch, give the revs a healthy blip and snick the lever up. I got more gears selected than false neutrals taking this approach and will continue to refine my technique. I also came to the conclusion that there's no point changing into first before the bike has stopped as it will pull from a very low speed in second.
My gear box does not have such trouble. I even can go to first before stopping. So, following your description I would consult other drivers, as well. Perhaps I am wrong but it smells as if something isn't in order. Maybe the attached texts help a bit.
Cheers, Thomas
Thomas, these documents are fascinating and very helpful in visualising how everything fits together. I'm wondering whether the selector pawl is worn or misaligned (maybe someone tightened the rivets but didn't have everything properly jigged). I suspect the work involved in resolving the problem is beyond my mechanical capabilities, but I'll see if I can find a mechanic within reasonable distance who can investigate. Thanks again for your help.
Indeed, overhauling the gearbox is somewhat delicate... but it is doable even for non-experts, I think. That was my situation with a rudimentary and very small workshop when overhauling my motor (see "1937 Sunbeam Model 9 Engine Overhaul" in the club website). I was brave enough to start the job... and was successful. But consulting an expert workshop (if you can find one) is a good option, of course.