Triumphrat

scarface · 05-15-2008

I need some help. I have a 68 Triumph 650 chopper with a 4 speed tranny. This tranny has got to go. 50 mph is painful and it sounds like it might blow up.
I have heard a 5 speed is available. How difficult is the the conversion? My son is an excellent mechanic but new to Triumphs. The bike is 'supposed' to be a 68 but the manual provided w/ the bike says 1970. How can I tell which engine, or year it is? Where can I get the the 5 speed kit?
Any other info regarding this kit/conversion will be greatly appreciated.
Jeff

GrandPaulZ · 05-15-2008

The serial number will tell you what year it is.

Either way, most Bonnies can go 70 without falling apart; the fact that yours feels "off" at 50 indicates that you have issues NOT transmission related.

Could be someone installed a way-too-small engine sprocket and/or too large rear sprocket. Also could be you are experiencing clutch slippage.

Emanthehorse · 05-16-2008

Top gear with a 5 speed is still 1:1 ratio, the same as a four speed.

There is no "kit" that I know of for this, you have to find a used 5 speed (good luck) and then do the conversion yourself. It's not rocket science, basically the indexing camplate will be fun with the three selector forks and I think the output bearing is different.

It will be WAY cheaper to adjust your gearing a little with a larger front, or smaller rear sprocket.

oldebonnie · 05-18-2008

I've been on the scout for a 5-speed for a while and in decent shape they are going for $500 minimum. Some case work may be required. Mecchanica has stated that the first couple of years of the 5-speed are not a desirable as later 5-speeds. I understand the swap out is not too difficult, but does require some skills.

Do a search on this site as I think the whole process has been discussed in the past. There is also an eBay seller who is selling a small text on doing the swap, so you could try looking there.

The real advantage of the 5-speed is that it permits a higher final drive ratio (lower numerically) while keeping first gear reasonably low (higher numerically).

GrandPaulZ · 05-19-2008

A 5-speed cluster (complete) went for $150 at the swap meet this weekend (I JUST missed it).

It had a mushroomed tip on the mainshaft, that could easily be welded up and re-threaded or just ground down and re-threaded. there were more than adequate threads that were not damaged. The rest of the box looked to be in near perfect condition.

too bad...

t100rc · 05-19-2008

Seriously ... the top gear of the 5 speed is the same as the top gear of the 4 speed.

All you gain thru this swap is more shifting.

Emanthehorse · 05-19-2008

Not entirely.

1st is lower with the 5 speed, so therefore you can gear up with the sprockets and effectively lower your cruising RPM without sacrificing your acceleration.

panda · 05-19-2008

AS it has been butchered into a chopper, do you have a Triumph rear wheel ? If so what size is it?
AS others have said, teh way to change final gearing is via the gearbox and wheel sprockets.

LJ3 · 05-19-2008

good point panda, I bet he has a 16" rear. I always liked the 4 speed better than the 5 speed. the 4 speed shifts like the AMC box with some space between the gears. to me the 5 speed feels too modern. scarface, if you were racing or doing some serious canyon carving the 5 speed makes sense. the good news is all you need is a new countersprocket, the bad news is you're going to tear down your primary drive to change it but its not too hard, sounds like a good project for memorial day weekend.

oldebonnie · 05-19-2008

"A 5-speed cluster (complete) went for $150 at the swap meet this weekend (I JUST missed it)."

$150?!! Did you cry over that one GPZ? Tears are welling up in my eyes just at the thought of missing out on a five-speed for $150. I gotta start going to swap meets.