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#859222 09/23/21 11:02 pm
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Is this about right? I lost my workshop manual which disappeared from my desktop. I am reading different figures from different sources. I had the needle off of the Smiths speedo so I need to get it right. Stock tires and sprockets, 5 spd '72 Tiger.

Second subject; On the freeways here (Lost Angeles) cruising at 4000 RPM in the "slow lane" (right-most) will still get you run off the road or rear-ended by a truck not to mention that the right lane is usually the most torn up from the heavy truck traffic. You also deal with people getting on and off at various speeds. To cruise in a "faster" lane I would need to sustain an RPM of more like 4500-4600+. This just doesn't feel right to me. I'm thinking that these engines were not designed for this. I remember the 60's-70's and I still drive a '69 GMC with a Chevy 350 (5.7L). Back then one would only hold an engine at 4000 if it was a temporary duration climbing a hill pulling a trailer (caravan?) or something or on a bike, just a short spurt of speed for some reason.Piston speed seems to be a major factor in engine wear. I try to avoid freeways but what do you guys think about holding 4600 RPM on a 49 year old Triumph with 21K miles on the odo. -Brian


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You can put a 21 gearbox sprocket on, it'll drop rpm at 70mph to around 4200.
I did it on my '69 but went back to 20 as i like the livelier acceleration. That's done
around 42k miles. These old things were designed to rev and will last very well if
built properly. You can't really compare them to a v8 car lump. 20-30k miles is
what you expect from engine rebuilds.
My 2c.

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I did 80 MPH from Carmel by the Sea to Cambria Ca. on the Coast Highway. 100 miles.
I held almost 100 MPH for 42 minutes in Nevada. The distance between two dots on the map.
No special sprockets. I don't much look at RPM. If you know and trust your bike they don't mind some high speeds. Better then being run over by a truck.
You forget, this motor, in it's day, set more land speed records and won more races than all other motorcycles combined.

You know how many Harley's I passed on that hundred mile ride?

All of them..

Ha ha. Old Norton Club joke.

Last edited by desco; 09/23/21 11:52 pm. Reason: addition

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The 72 manual I have shows 659 rpm for 10 mph, so 60 mph would be 3954 rpm, so it sounds about right.
Of course when the rear tyre wears, it takes more rpm for a given speed.

I’ve never thought Triumph 650’s were shy of doing steady motorway speeds (70mph in the UK). My late 50’s pre-unit copes with that ok (~4500 rpm in my case, a little more in yours). That shouldn’t be a worry, unless the engine isn’t up to scratch.

Using 6500-7000 frequently or continuously on an old engine is another matter, and depends on your approach. I prefer not to. I don’t know the precise maths, but I suspect 6500 rpm over 4500 rpm is at least 4 times the mechanical stresses on the crank and rods.

Just thoughts.

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Seems about right

My 68' TR6 does about 65 @4,500 RPM approx

I think I have an 18T fitted

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I have an Excel spreadsheet file that can calculate your speed based on variables you plug in. Pretty sure Malcolm (sp?) Britbodger R.I.P. sent to me. If you'd like a copy DM me you email address.

Cheers,

Steve

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Originally Posted by NickL
You can put a 21 gearbox sprocket on, it'll drop rpm at 70mph to around 4200.
I did it on my '69 but went back to 20 as i like the livelier acceleration. That's done
around 42k miles. These old things were designed to rev and will last very well if
built properly. You can't really compare them to a v8 car lump. 20-30k miles is
what you expect from engine rebuilds.
My 2c.
Thanks. Definitely thinking about the 20 tooth sprocket next time I go into the clutch (rubber shock absorber replacement). OK, I won't worry about it too much but according to your guideline I should be due for a rebuild soon. -Brian


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Originally Posted by desco
I did 80 MPH from Carmel by the Sea to Cambria Ca. on the Coast Highway. 100 miles.
I held almost 100 MPH for 42 minutes in Nevada. The distance between two dots on the map.
No special sprockets. I don't much look at RPM. If you know and trust your bike they don't mind some high speeds. Better then being run over by a truck.
You forget, this motor, in it's day, set more land speed records and won more races than all other motorcycles combined.

You know how many Harley's I passed on that hundred mile ride?

All of them..

Ha ha. Old Norton Club joke.

HaHa! You must have a pretty tight machine there. I think mine would vibrate apart if I even got it up to 100.It struggles at 80 and I need to sort out the mixture before I can go flat out for any length of time.


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Originally Posted by koan58
The 72 manual I have shows 659 rpm for 10 mph, so 60 mph would be 3954 rpm, so it sounds about right.
Of course when the rear tyre wears, it takes more rpm for a given speed.

I’ve never thought Triumph 650’s were shy of doing steady motorway speeds (70mph in the UK). My late 50’s pre-unit copes with that ok (~4500 rpm in my case, a little more in yours). That shouldn’t be a worry, unless the engine isn’t up to scratch.

Using 6500-7000 frequently or continuously on an old engine is another matter, and depends on your approach. I prefer not to. I don’t know the precise maths, but I suspect 6500 rpm over 4500 rpm is at least 4 times the mechanical stresses on the crank and rods.

Just thoughts.

Thanks. Looks like another vote for "Don't worry, go fast".

I shift at about 6500 when I'm "in a hurry" but I would never dream about holding it there. I did, on a modified '69 Bonnie, 120 (indicated) and later it let go while putting around. I had to put an up an ad and found a replacement in perfect shape for $50.-early 80's-

Last edited by BAinLA; 09/24/21 3:44 am.

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Originally Posted by C.B.S
Seems about right

My 68' TR6 does about 65 @4,500 RPM approx

I think I have an 18T fitted

Sounds like it. So you cruise at 65. I could see doing that and living a long life. Just hoping this old relic will do the same.

Last edited by BAinLA; 09/24/21 3:40 am.

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Originally Posted by JubeePrince
I have an Excel spreadsheet file that can calculate your speed based on variables you plug in. Pretty sure Malcolm (sp?) Britbodger R.I.P. sent to me. If you'd like a copy DM me you email address.

Cheers,

Steve

Thanks Steve. Actually that page you posted showing the 20 tooth speeds is all I need. So 64.47 at 4K with the 20. Looks good to me.

Last edited by BAinLA; 09/25/21 2:07 am.

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Hi Brian, I’d strongly recommend 20t in front. 21 certainly lowers rpm more bu motor will tend to lug, forcing sooner down shifting.
With 20t on front you’ll find comfortable cruising 62-64. I certainly understand about trucks & cars breathing down your neck. Sadly freeway is fact of life for us.

I’ve observed they owners that rev motor to red line 7000 often & cruise at high speeds the motor doesn’t last long. 5-10 k miles. 15k if they are lucky. They seem to do ok at 4500. I’ve observed tachs tend to read higher than true rpm above about 3500.

However…. Getting your mixture correct is a top priority. Lean mixture will kill the motor even worse than higher rpm at 75 mph. Mixture is your top priority. Timing must be good also. You might find 36b works a little better.
Top grade full is important. Never use low or mid grade. Chevron or Shell 91 seems best.

Regarding mixture. Start with float level using manometer tube. Next set main jet. Go larger until you get 8 stroking. Then go smaller to next size. You’ll probably want needle clip on bottom groove. Running lean is a disaster.
Don


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I don't know. My engines seem to last forever. Never blown one up. Do the rings every now and then. Do the valves about every third ring job, needed or not.
Used to ride a LOT. At 77 not so much. Still too fast and too hard. That's what they are for.


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koan

If everything inside the engine is brand new it's not and old engine. It's a new engine. Old design, but one that worked pretty well.


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Originally Posted by TR7RVMan
Hi Brian, I’d strongly recommend 20t in front. 21 certainly lowers rpm more bu motor will tend to lug, forcing sooner down shifting.
With 20t on front you’ll find comfortable cruising 62-64. I certainly understand about trucks & cars breathing down your neck. Sadly freeway is fact of life for us.

I’ve observed they owners that rev motor to red line 7000 often & cruise at high speeds the motor doesn’t last long. 5-10 k miles. 15k if they are lucky. They seem to do ok at 4500. I’ve observed tachs tend to read higher than true rpm above about 3500.

However…. Getting your mixture correct is a top priority. Lean mixture will kill the motor even worse than higher rpm at 75 mph. Mixture is your top priority. Timing must be good also. You might find 36b works a little better.
Top grade full is important. Never use low or mid grade. Chevron or Shell 91 seems best.

Regarding mixture. Start with float level using manometer tube. Next set main jet. Go larger until you get 8 stroking. Then go smaller to next size. You’ll probably want needle clip on bottom groove. Running lean is a disaster.
Don

Hi Don, I've heard somewhere that the 20t isn't available for my '72 5spd.I'll have to search further when/if the time comes that I go into the clutch.
Piston speed is definitely a factor in engine life expectancy. Witness the modern engines cruising at 1800 RPM @ 60 MPH lasting forever.

I'm running 91 Octane mixed with 100 Octane race gas. I just raised the needle to it's richest setting which seems to have cured the stumble. I still find that it runs better with the choke slightly closed, due perhaps from the worn slide/bore situation (22K miles). At full throttle is seems a little flat, a little weak. But then my last bike was a freshly rebuilt Bonnie with multiple upgrades running on 1980 gasoline. Do you think I should try bigger than .230 main? Float is to spec without using the nanometer method. Timing is set to spec but I might bend the tangs a wee bit to raise the advance action up the RPMs slightly. Thanks, Brian


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Originally Posted by desco
koan

If everything inside the engine is brand new it's not and old engine. It's a new engine. Old design, but one that worked pretty well.

Actually everything inside this engine is original. It smokes something awful once in a while at start-up due, I imagine, to worn guides. No smoke during operation. I would guess that it could use a rebuild but compression is excellent so maybe just the valves.


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Hello; if you do not pass the 70% of what max RPMs is supposed to be, you are not hurting the engine. In a 750 4000 is not hurting anything. I see that the 650 s feel a bit busy; do not not why but you are not hurting anything. Also; is better to use the engine in a wider range of RPMs

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Originally Posted by BAinLA
Originally Posted by C.B.S
Seems about right

My 68' TR6 does about 65 @4,500 RPM approx

I think I have an 18T fitted

Sounds like it. So you cruise at 65. I could see doing that and living a long life. Just hoping this old relic will do the same.


The open roads out here in Lancaster sometimes FORCE me to do 75-80 on the freeway

I should go up to a 19T but then sometimes I do canyon riding WITH a passenger

I'm good with 18T

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Originally Posted by C.B.S
…sometimes I do canyon riding…

Little jealous… clap

Steve


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Hi BA, I know this for certain. 20t for ‘72 5 speed is readily available. I’d have to check ‘72 part book #, but using part # from ‘73 parts book will fit. I prefer the repro with 2 threaded holes as it allows use of a puller to remove if needed.

Spline inside 5 speed sprockets is all the same, as is nut. There is an early & later sprockets. The later sprocket has chamfer on outer end of splines for oring. However to use the oring the 5th gear snout/spline has groove cut for oring, & lock tab washer is different to accommodate oring.

Unless your 5 5th gear was replaced with latest version you won’t use oring, but later sprocket with chamfer will fit fine.

You can use later sprocket as a direct replacement, reusing tab washer & nut. However an early tab washer cannot be used on late 5th gear with oring groove as the inner tab is in thin air due to groove.

The 5 speed sprocket tends to seep at the spline. My ‘73 Tiger had Loctite from factory. Even with oring I’d still use some sealant.


Seal depth is important. Too far out it rubs sprocket, too deep lip misses seal race on sprocket. Look how deep your old one was.

There is 2 versions of early 5th gears. Difference is width of bearing race, but sprocket & spline is the same. Again spline is same on late 5th gear. But it got groove for oring.

All this can be confusing. I have the ‘73 & late versions in hand. If you had them in hand it all makes sense & becomes simple.

Triumph never posted sprocket nut torque until 1982 shop manual. 80#. That would apply to all 5 speeds in my mind. The BSA manual for triples showed 70# as I recall. So use 70 or 80, your choice

On an aside Triumph finally posted torque for swing arm pivot bolt 60#. Rear axle 60#.

Regarding main jet I would absolutely go one step larger. If you’re lucky you can remove jet with deep 8mm socket through bowl drain. Usually the jet holder comes loose so you need to remove bowl. I also give it a try with deep socket though.

Here’s accurate main jet test. Suppose your going north on the 405 up the hill. 65-70 mph. Roll on full throttle. If too rich when you get above 3/4 throttle the motor will 8 stroke. Ah ah ah. Will scare you! Backing off instantly goes away. Rolling throttle on it instantly comes back. Again back off throttle it’s good. It only takes a few moments & you learn when main jet comes into play.

I have a lot of practice. Very hard to feel lean main jet. That’s why I go too rich until 8 stroke, then one step smaller. I’ll just tell you it works well with our fuel. I bought a selection of main jets. The cost of tuning. Obviously tuning is very time consuming!! Takes all day or several days depending on traffic & how far you need to travel to get to suitable test road. It takes time & practice to learn the sound & feel of tuning. Doing it is the only way to learn this.

I don’t recall did you check float level with the manometer? If float level is off, you will chase your tail forever.

I have experience with worn slides/bores. Running down the highway slide wear has minimal effect. That is my experience.

Needle wear is a problem. The needle wears skinnier in area where we ride most. 1/16-1/8 throttle. So it’s passing more fuel. Runs good, but leaving worn area with more throttle is may go lean. Or it’s too rich in wear zone & good at not worn zone.
The needle jet wears also.

Gets complicated fast! Thing is the factory specs are for 1972 100 octane leaded. With California E10 91 factory specs are out the window. I found after many tests even 1/4 91 to 3/4 race gas didn’t work nearly as well as 100% race gas.

If you get mixture right set timing to 36 before you won’t need race gas. Fitting EI will greatly reduced ping & bike will run a little better at speeds under 3500 rpm.

These motors were high performance in a bygone day. These bikes are very usable today, but you must accommodate for modern fuel & traffic. I know this is possible. My close riding circle of friends have done it.
Don


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Bonnevilles weren't made to chug around at below 3k rpm

Although many bikes are not exactly young, they are probably better looked after now than 10 years after being made.

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Originally Posted by AngloBike
Bonnevilles weren't made to chug around at below 3k rpm

Although many bikes are not exactly young, they are probably better looked after now than 10 years after being made.

Yeah I tend to keep the revs at or above 3000. Since I got this thing on the road I've been changing the oil frequently and trying to take real good care of it.


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Originally Posted by TR7RVMan
Hi BA, I know this for certain. 20t for ‘72 5 speed is readily available. I’d have to check ‘72 part book #, but using part # from ‘73 parts book will fit. I prefer the repro with 2 threaded holes as it allows use of a puller to remove if needed.

Spline inside 5 speed sprockets is all the same, as is nut. There is an early & later sprockets. The later sprocket has chamfer on outer end of splines for oring. However to use the oring the 5th gear snout/spline has groove cut for oring, & lock tab washer is different to accommodate oring.

Unless your 5 5th gear was replaced with latest version you won’t use oring, but later sprocket with chamfer will fit fine.

You can use later sprocket as a direct replacement, reusing tab washer & nut. However an early tab washer cannot be used on late 5th gear with oring groove as the inner tab is in thin air due to groove.

The 5 speed sprocket tends to seep at the spline. My ‘73 Tiger had Loctite from factory. Even with oring I’d still use some sealant.


Seal depth is important. Too far out it rubs sprocket, too deep lip misses seal race on sprocket. Look how deep your old one was.

There is 2 versions of early 5th gears. Difference is width of bearing race, but sprocket & spline is the same. Again spline is same on late 5th gear. But it got groove for oring.

All this can be confusing. I have the ‘73 & late versions in hand. If you had them in hand it all makes sense & becomes simple.

Triumph never posted sprocket nut torque until 1982 shop manual. 80#. That would apply to all 5 speeds in my mind. The BSA manual for triples showed 70# as I recall. So use 70 or 80, your choice

On an aside Triumph finally posted torque for swing arm pivot bolt 60#. Rear axle 60#.

Regarding main jet I would absolutely go one step larger. If you’re lucky you can remove jet with deep 8mm socket through bowl drain. Usually the jet holder comes loose so you need to remove bowl. I also give it a try with deep socket though.

Here’s accurate main jet test. Suppose your going north on the 405 up the hill. 65-70 mph. Roll on full throttle. If too rich when you get above 3/4 throttle the motor will 8 stroke. Ah ah ah. Will scare you! Backing off instantly goes away. Rolling throttle on it instantly comes back. Again back off throttle it’s good. It only takes a few moments & you learn when main jet comes into play.

I have a lot of practice. Very hard to feel lean main jet. That’s why I go too rich until 8 stroke, then one step smaller. I’ll just tell you it works well with our fuel. I bought a selection of main jets. The cost of tuning. Obviously tuning is very time consuming!! Takes all day or several days depending on traffic & how far you need to travel to get to suitable test road. It takes time & practice to learn the sound & feel of tuning. Doing it is the only way to learn this.

I don’t recall did you check float level with the manometer? If float level is off, you will chase your tail forever.

I have experience with worn slides/bores. Running down the highway slide wear has minimal effect. That is my experience.

Needle wear is a problem. The needle wears skinnier in area where we ride most. 1/16-1/8 throttle. So it’s passing more fuel. Runs good, but leaving worn area with more throttle is may go lean. Or it’s too rich in wear zone & good at not worn zone.
The needle jet wears also.

Gets complicated fast! Thing is the factory specs are for 1972 100 octane leaded. With California E10 91 factory specs are out the window. I found after many tests even 1/4 91 to 3/4 race gas didn’t work nearly as well as 100% race gas.

If you get mixture right set timing to 36 before you won’t need race gas. Fitting EI will greatly reduced ping & bike will run a little better at speeds under 3500 rpm.

These motors were high performance in a bygone day. These bikes are very usable today, but you must accommodate for modern fuel & traffic. I know this is possible. My close riding circle of friends have done it.
Don

Very good info here thanks a lot. I guess I will be sourcing a bigger main jet or 2 and play around with these to see what happens.

I tried retarding the spark and was not pleased with the drop in power thus the race gas. Still looking for some top-end performance and I think your idea of a bigger main might just be the ticket. For now I am going to stick with points ignition which have been working very well. All in all the bike performs excellently but I do remember them having more power than I am experiencing now. -Brian


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Originally Posted by desco
I don't know. My engines seem to last forever. Never blown one up. Do the rings every now and then. Do the valves about every third ring job, needed or not.
Used to ride a LOT. At 77 not so much. Still too fast and too hard. That's what they are for.

Desco, that;s very encouraging. I won't worry about it anymore. It's really not that difficult to work on these things anyway really. Thanks, Brian


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