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| pedro750 |
 Posted: Mon Feb 16, 2009 3:25 pm |
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Member
Joined: 16 Jan 2006
Posts: 48
Location: Italy
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Dear friends, I need help about gearbox.
On my "750" I've a big problem: when power arives at 5500 rpm 4° gear slips out... This's a drama! I can't use all the 4° gear. So I decided to open the engine and I've found the 4° disaster... Rounded dogs. I've to check forks but I think that they aren't in good conditions...
So, I have 3 or 4 engine in my box and I want to know if its possible use an F1 engine’s gearbox on a K1's engine, from the shop manual I've sow that F1 has:
- Primary reduction is different. (Shorter than K1)
- 1°, 2° and 3°: have the same ratio.
- 4°: have a different ratio. (Shorter than K1)
- 5°: have a different ratio. (Longer than K1)
The clutch box are compatible?
The transmission mainshaft and countershaft are compatible?
The bearings are compatible? |
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| Voxonda |
| Posted: Mon Feb 16, 2009 7:29 pm |
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Member
Joined: 01 Nov 2006
Posts: 42
Location: The Netherlands
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Hey pedro,
Must say I've never interchanged gearboxes, but IMHO think it allright to do so. Like you have seen, you're gears are somewhat different in ratio, but that is not a problem.
Good luck and keep us informed, please.
Cheers, Rob |
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| Satanic Mechanic |
| Posted: Tue Feb 17, 2009 7:19 pm |
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Moderator
Joined: 04 Sep 2005
Posts: 309
Location: Munich, Germany
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As long as you change the complete gearbox, you should be allright. The final drive shaft may be different, then you will have to use the old one (which should not be a problem). The clutches are interchangeable. It should be pretty much straightforward.
All the best,
Axl |
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| pedro750 |
| Posted: Wed Feb 18, 2009 9:11 am |
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Member
Joined: 16 Jan 2006
Posts: 48
Location: Italy
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Thanks at all. In this w-e I'll work on it and I'll try to post some pictures.
Kind regards at all!
Pedro |
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| fang |
| Posted: Thu Feb 19, 2009 6:07 pm |
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Junior member
Joined: 19 Oct 2005
Posts: 23
Location: Austin, Texas, USA
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Another option is to get the gears "back cut." The do this on many race engines -- they put a slight positive angle on the gear dogs so that the gears lock together more strongly. This costs about to back cut a set of gears and many machine shops will do it.
-fang |
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| pedro750 |
| Posted: Fri Feb 20, 2009 9:03 am |
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Member
Joined: 16 Jan 2006
Posts: 48
Location: Italy
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fang wrote: Another option is to get the gears "back cut." The do this on many race engines -- they put a slight positive angle on the gear dogs so that the gears lock together more strongly. This costs about to back cut a set of gears and many machine shops will do it.
-fang
This's an option that I'm studing and probably I'll do by myself...
Today I'll return at home and I'll start to see various gearbox that I've at home, I'll do measurament adn I'll decide. So I'll try to back cut.
I'll try to post some photos too. |
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| fang |
| Posted: Fri Feb 20, 2009 7:17 pm |
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Junior member
Joined: 19 Oct 2005
Posts: 23
Location: Austin, Texas, USA
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I think it is very doable at home by a skilled craftsman. The trick is consistency. You want the exact same angle and the exact same amount of metal removed from each gear dog. If you set up a rig to do it, you can do it right. Most people only back-cut the dogs, but some will do the leading/front edge too for engine braking as well as acceleration.
Here is a random pic I saw on the internet:
I'm sure you will research before you start cutting!
Best of luck to you!
-fang |
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| pedro750 |
| Posted: Tue Feb 24, 2009 3:05 pm |
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Member
Joined: 16 Jan 2006
Posts: 48
Location: Italy
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Thanks Fang,
yes did a lot of reserch and the most intrasting answer about back cut I've found on SOHC4.com
I can work with lang for a good cut |
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| pedro750 |
| Posted: Wed Mar 11, 2009 12:12 pm |
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Member
Joined: 16 Jan 2006
Posts: 48
Location: Italy
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So,
the situation is this:
I've cheked all engins I've and I fund that the gearbox from SS (F1) is different from the standard specifications:
The primary reduction, 1° gear, 2°gear, 3° gear, 5° gear are the same if comparated with K1 gears-ratio.
The only diference is the 4° :
- 1.097 K1,
- 1.133 F1,
and final reduction:
- 1.097 K1,
- 1.133 F1.
So I'll follow this combination:
I'll replace all the K1's gear box with F1's gearbox but I'll mantain the K1's reduction (more shorter than the F1).
The F1's gearbox has 20000 km and is in very good conditions, the dogs are good, so 90% I'll don't undercut them. I'll use all F1's parts about gearing system.
Stay tuned  |
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