A A A
Avatar

Please consider registering
Guest

Search

— Forum Scope —






— Match —





— Forum Options —





Minimum search word length is 3 characters - maximum search word length is 84 characters

Register Lost password?
sp_Feed sp_PrintTopic sp_TopicIcon
4 speed box question
Avatar
Colin1
Glasgow, Scotland UK
Second Gear User
Club Member
Forum Posts: 23
Member Since:
February 4, 2020
sp_UserOfflineSmall Offline
1
October 21, 2020 - 3:05 pm
sp_Permalink sp_Print

I have been riding my Bantam D10 sports after a rebuild. Problem was that I couldn't get 4 gears. I thought, "I've made an error during reassembly, only solution is to disassemble and check it out." So here I am with the gear box exposed in front of me. I now find the gear box is changing much smoother and I am getting all four gears. I haven't done anything to fix it. So I think the problem is only apparent after the cranks are together. 

Any ideas why this might be? Could the gear change spring be too weak? See picture. Is the gap between the gear level and kickstart splines OK. See picture. 

I have turned the mainshaft using the clutch basket in all gears and each gear works to drive the output shaft.. and neutral works too. 

Yes it is puzzling. 20201021_143745_resized1.jpg20201021_143741_resized1.jpg

Avatar
cocorico
Central France
Top Gear User
Site Member
Forum Posts: 3292
Member Since:
June 23, 2013
sp_UserOfflineSmall Offline
2
October 21, 2020 - 4:36 pm
sp_Permalink sp_Print

Could be a slight misalignment when you put the case halves together. Have you got the locating dowels properly fitted? Or a bearing, or bush could be not quite seated, causing a problem when under tension. You could try putting it together and tightening the screws progressively to see when it starts to give trouble.

Avatar
stubaker58
Sunny Felixstowe
Area Rep
Club Member
Forum Posts: 561
Member Since:
June 13, 2015
sp_UserOfflineSmall Offline
3
October 21, 2020 - 5:17 pm
sp_Permalink sp_Print

Funnily(!?) enough I’ve just had the exact same problem. All back together, it started but no top gear. I did replace the layshaft bushes so maybe they’re tight? When I summon the energy it’s engine out time again.

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

Avatar
AdrianS
Harlaston Staffs
Top Gear User
Club Member
Forum Posts: 155
Member Since:
August 8, 2014
sp_UserOfflineSmall Offline
4
October 22, 2020 - 5:41 pm
sp_Permalink sp_Print

What did the rebuild consist of?

I rebuilt my D14 a couple of years ago; new bearings and seals, reborn, replacing other worn bits such as clutch plates primary chain etc. First ride out and 4 th gear kept jumping out. Ended up stripping the engine again and buying a new sliding pinion and having the output gear being rebushed which sorted it out. Funny that I had no trouble with the gearbox before the rebuild!

Avatar
Colin1
Glasgow, Scotland UK
Second Gear User
Club Member
Forum Posts: 23
Member Since:
February 4, 2020
sp_UserOfflineSmall Offline
5
October 26, 2020 - 7:50 pm
sp_Permalink sp_Print

I have got the gears running through 1st to 4th now but not consistently. Moving from 3rd to 4th or 4th to 3rd results in the cam sometimes sticking midway between the two gears. Trying to move the gear lever further up to click into the 4th cam slot Is impossible but if I drop down partially and up agian it travels to the 4th cam. This is driving me mad. I keep thinking maybe it will be OK when the engine is running. But I don't want to reassemble the bike again until I am sure everything is OK. I'm thinking could it be the gear lever return spring? 

Any advice to point me in the right direction? 

Avatar
cocorico
Central France
Top Gear User
Site Member
Forum Posts: 3292
Member Since:
June 23, 2013
sp_UserOfflineSmall Offline
6
October 26, 2020 - 9:11 pm
sp_Permalink sp_Print

The gearchange requires a good 'positive movement to take you through the dead points, easy enough on the move but more difficult static. I find that it is better to rotate the output pinion whilst moving the lever through the gears, rather than through an unmoving box (not easy to describe though...)

Avatar
chippy
medway
Top Gear User
Club Member
Forum Posts: 119
Member Since:
April 9, 2015
sp_UserOfflineSmall Offline
7
October 26, 2020 - 9:17 pm
sp_Permalink sp_Print

Hi Colin, I had much the same trouble awhile back, rightly or wrongly I changed to a straight 30 oil which I found improved it slightly but still occurs from time to time, and also found a much cleaner change 3rd to 4th without the clutch, hope it works for you !

Chippy

Avatar
Colin1
Glasgow, Scotland UK
Second Gear User
Club Member
Forum Posts: 23
Member Since:
February 4, 2020
sp_UserOfflineSmall Offline
8
October 27, 2020 - 4:04 pm
sp_Permalink sp_Print

Thanks for all the inputs everyone. I guess I am expecting too much and hoping for a silver bullet that will give me a slick gear change. Surprisingly the more I mess with the gears the better things seem to get. So I'll reassemble and hope for the best. 

Avatar
Colin1
Glasgow, Scotland UK
Second Gear User
Club Member
Forum Posts: 23
Member Since:
February 4, 2020
sp_UserOfflineSmall Offline
9
November 9, 2020 - 2:21 pm
sp_Permalink sp_Print

I have stripped the gears out to look at all the components. I found some corrosion and tight spots on the selector shaft and have fitted a clean one. However, I decided to replace the indent spring and ball bearing while I was at it. The replacement bearing is .375" but the one that was in the gearbox was .312". The engine is a D10A 4 speed for my D10 Sports.

I have a B175 engine in bits as well and I see its bearing is .375". The cams are identical. Anyone know if I can safely fit the new .375" ball bearing? Or why the D10 sports engine should have a smaller ball bearing? 

Avatar
GlenAnderson
Dover
Top Gear User
Club Member
Forum Posts: 247
Member Since:
August 27, 2013
sp_UserOfflineSmall Offline
10
November 9, 2020 - 2:42 pm
sp_Permalink sp_Print

I think the 0.375” (3/8”) is the right size. Your D10 engine having a smaller 0.312” (5/16”) one is likely down to a previous owner’s error. 

Avatar
Alan.Moore
Leicestershire
Top Gear User
Club Member
Forum Posts: 166
Member Since:
April 10, 2020
sp_UserOfflineSmall Offline
11
November 9, 2020 - 6:08 pm
sp_Permalink sp_Print

Colin1 said
I have got the gears running through 1st to 4th now but not consistently. Moving from 3rd to 4th or 4th to 3rd results in the cam sometimes sticking midway between the two gears. Trying to move the gear lever further up to click into the 4th cam slot Is impossible but if I drop down partially and up agian it travels to the 4th cam. This is driving me mad. I keep thinking maybe it will be OK when the engine is running. But I don't want to reassemble the bike again until I am sure everything is OK. I'm thinking could it be the gear lever return spring? 

Any advice to point me in the right direction?   

Have recently rebuilt mine and had exactly the same issue trying it static. I was convinced I had rebuilt it correctly and had been able to get all gears fully engaged before the cases went back together. I did find that turning the output sprocket whilst changing gears improved things. Have now had the engine running and the gears all engage fully and repeatedly. 

Re the detent ball, my B175 is also 0.375" and Drags show it as 3/8" for the D10 and B175...same part number

Cheers

Alan

1939 Ariel VH, 1942 Ariel WNG, 1951 Triumph 6T Thunderbird, 1970 BSA Bantam B175, 1980 Honda CB250N, 1986 Yamaha SRX600

Avatar
Colin1
Glasgow, Scotland UK
Second Gear User
Club Member
Forum Posts: 23
Member Since:
February 4, 2020
sp_UserOfflineSmall Offline
12
November 9, 2020 - 6:53 pm
sp_Permalink sp_Print

I think I finally have fixed my gearbox and on the bench the gears are changing smoothly. I think the main cause has been the return gear change spring. I have discovered that one leg of the spring is too long and rubbing on the selector cam. Now and again it catches in a hole in the back of the cam. I have fitted another spring from my box of bits and this allows a clearance between the spring and the cam. I'll post a picture of the spring later. 

So the problem could have been due to all three of the faults I have found.received_452965282352725.jpeg

sp_PlupAttachments Attachments
Avatar
Colin1
Glasgow, Scotland UK
Second Gear User
Club Member
Forum Posts: 23
Member Since:
February 4, 2020
sp_UserOfflineSmall Offline
13
November 9, 2020 - 6:55 pm
sp_Permalink sp_Print

Thanks everyone for your help.

Avatar
stubaker58
Sunny Felixstowe
Area Rep
Club Member
Forum Posts: 561
Member Since:
June 13, 2015
sp_UserOfflineSmall Offline
14
November 23, 2020 - 7:12 pm
sp_Permalink sp_Print

Well I finally plucked up courage and took the engine out of my bike too.  To recap it ran but fourth gear was (mostly) absent.  When I got it apart it became clear that the selector claw was not returning to locate properly on the selector cam lugs after third was selected.  After some cogitation I worked out that a gentle down pressure allowed fourth to be selected.  

With great advice from another Suffolk Bantamite it turned out that the return spring tangs were angled too much, this meant that the fixed lug forced the spring open and made it (slightly) loose on the lug on the spindle.  I replaced the original spring which has straighter tangs and these grip the spindle lug tightly, giving a small amount of play on the fixed lug.  Problem solved!

Engine back in bike, just the final few bits and bobs to sort then a further test run. (I’ve also upped the oil in the petrol as I’m running in a newly rebored barrel with big bore piston and last time out had a minor seizure).

Thanks Colin for the thread.

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

Forum Timezone: Europe/London

Most Users Ever Online: 223

Currently Online:
6 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Top Posters:

cocorico: 3292

Cornish Rooster: 3109

bart: 2688

Blue Heeler: 2546

David Dale: 2349

Sprung Chicken: 2301

Piquet: 2063

Mags 1: 1863

jess steele: 1674

sunny: 1657

Newest Members:

carmencc11

Forum Stats:

Groups: 9

Forums: 48

Topics: 11009

Posts: 97748

 

Member Stats:

Guest Posters: 1433

Members: 3003

Moderators: 0

Admins: 3

Administrators: Bantam-Super, JMD, Stoo63