Triumphrat

Spartacus · 03-06-2008

Hi everyone,
This is my first post on this forum. I have just been given wifely approval to look for a Bonnie to rebuild. I have never worked on a bike before just old cars mainly Triumphs but I dont have the space for a classic car rebuild so I have always really liked Bonnevilles and Tridents. So I am going to look at a Bonnie this weekend. The guy selling it says its a 1971 Bonnie with a 1968 650cc engine but with a single carb. He seemed to think that the engine was a Bonneville but unless its been converted to a single carb am I right in thinking that it might be a bitza with a Trophy engine. So I have a few questions.
How important is it to have matching numbers as far as keeping resale value after a rebuild?
If this is a Bonneville engine with a single carb manifold, how can I tell and how much am I looking at to convert back to twin carbs? I am keen to have the bike as close to original as possible by the end of the rebuild.
Are the 1971 Bonnevilles all "oil in frame" and is it best to avoid these i.e. are these a bundle of trouble, so would it be best to wait until a pre-1970 model comes along.
By the way this is a great forum, just the right balance of info, fun and disagreement. Keep it up.

Mike

Tre900 · 03-06-2008

You need to post the seral number to tell what the bottom end is. If he's saying its a bonnie he must mean the bottom end and possiblity the barrels.

A single carb Cylendar head is a "trophy" which is a TR6. I need a single carb Cylinder head so if you find a double and need to get rid of this one look me up.

As for matching numbers it is the ideal situation to retain rebuild value. It depends on how nuts you want to go with the rebuild and what your ultimitly looking for.

If you want this to turn a profit then yeah, you will want matching frame and engine. If you watn this for yourself and personal pride, then I would suggest finding out if your STATE DMV will title something that doesn't have matching numbers. That's the real biggie.

Posting the engine #'s will get you a lot of answers as well as the frame #'s.

GrandPaulZ · 03-06-2008

For the bike you are describing, the serial numbers are of no importance other than for ONE of them to match the registration paperwork.

There are pros and cons to earlier and later models, none of any significance on this particular bike.

Personally, I am biased towards the "dry frame" (oil tank, pre-71) models; that has nothing to do with thier virtues or vices.

If you are looking at a decent running bike, expect to pay $2,500.00. If you get it for less, you got a good deal; if he's asking more, you might look around more.

quagmire · 03-06-2008

Quote:

How important is it to have matching numbers as far as keeping resale value after a rebuild?

Matching numbers mean nothing if you never plan to sell it. If you want to sell it at a later date and get top dollar, you need matching numbers. It doesn't mean a non matching machine isn't good, just resale is better with matching numbers a to certain audience.

TBS · 03-06-2008

Always check the 3 numbers stamped on the boss underneath the engine on each side of the cases where the main through bolt goes, they should match, eg. 375 on both sides, otherwise you have an engine that has had a serious blow up.

abmar · 03-06-2008

I rode a 71 Tiger 650 for many years and miles. All 71s are oil in frame. There is absolutely nothing wrong with them, they probably handle better than previous years but have the same motor. People complain about the conical front brake but it always worked well for me. The oif models have a lower oil capacity than earlier years and that is somewhat of a concern, especially if they are ridden hard or in hot temperatures.

If the motor came from a bonnie it should be stamped T120R after the serial number. A bonnie frame should also be stamped T120R at the steering head. Matching numbers make no difference to the way the bike runs but they do raise the resale value so pay accordingly. As far as the cylinder head goes, a bike with a single carb head is easier to maintain simply because you are only dealing with one carburetor and throttle cable. The dual cable setup makes it a pain to synchronize the carbs, resulting in a bike that will run worse than with a single carb. In any case, in practical terms there is very little difference in performance between the Tigers and Bonnevilles. Bonnies were sold as status bikes, Tigers were often chosen by serious riders.

Bruce Martin

Spartacus · 03-06-2008

Thanks very much for your advise everyone.
I'm due to look at this bike on Saturday so I will look for all those points and will get back to you with the actual numbers. I'm glad to hear that there are no problems with the OIF. So that does open the market out a bit when choosing a bike to rebuild. I will be doing this for my own satisfaction and will probably never sell it although I have told the missus otherwise, but I would like to bring it up to as near original as possible.
Cheers
Mike

GeoffE · 03-06-2008

Hi,

One piece of information, just in case it is relevant? '71 was the first year of the OIF frame, and was not well received as the seat height challenged alot of people. The frame was modified for '72 to give a lower seat height. Thus the '71 normally demands a discount compared to other years.

Personally I think the '71 is a superb frame (design input from Rob North, I believe), but may be a problem if you have short legs?

Ciao,
Geoff

GrandPaulZ · 03-06-2008

Your biggest consideration in maintenance should be VERY frequent oil changes, as the combination of slightly lower oil capacity and the crankcase oil being shared with the primary chain & clutch means that contamination accumulates at a faster rate than with the older models.

abmar · 03-06-2008

If it has a '68 motor the engine and primary drive will have separate oil supplies. The crankcase breather system wasn't changed until 1970. I am 5'8" and never had the slightest problem with the saddle height on my '71 Tiger. I didn't realize it was an issue until I read about it later.

Bruce Martin