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#817640 07/27/20 3:03 pm
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Hello all,

I’m in the middle of rebuilding the engine for my T140. This engine was completely stock when I took it apart and I have no intentions of making major performance enhancements to it, aside from 9.5:1 compression, spitfire cam, and a 3 piece roller bearing.

I’m wondering what people would do with the crankcase vent and primary. Is it advantageous to add the crank seal and separate the primary oil from the engine oil like the older engines were? Or should I just leave it alone and put it back the way it came apart. I really have no compelling reason to change things but now is the time to rearrange the breather and add the seal if I want to.

Thanks

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The previous camshaft timed version of the crankcase breather wasn’t up to the job on a 750 at speed.

There’s nothing wrong with the T140 breather.


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Thrasher +1
The timed breather even struggles with a 650 at sustained high rpm, though this only manifests as sweating at all the engine joints. In moderate use it isn’t a problem at all.

I don’t think this system was ever tried on a T140, as the chaincase breather arrangement was adopted 2 years or so before the 750s appeared.

However, many pre-70 650s have had 750 conversions put on them, but I haven’t any direct knowledge of how they cope with the timed breather.
It may be reasonable to suspect they might struggle even more than the 650 at sustained high rpm. (Stan Shenton in his 1972 tuning book was advising adapting pre-70 cases to the later system, for racing conditions).

If you were to blank off the small holes and install an oil seal, you would have to provide an alternative crankcase breather. One I think may be the best uses the front engine mount chamber. Holes are drilled through to the crankcase and a reed valve plumbed in the top.
Others have installed a vent on the timing cover, next to the inlet cam.

Either of these is possibly more trouble than you want to go to. As said, the T140 system works fine.

With my pre-unit 650 I am content to put up with the original timed breather and the minor sweating when used at sustained high rpm (which only happens on a motorway, say constant 4500+ rpm for hours) in exchange for the independence of the chaincase in terms of oil type and level (for best clutch performance).

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koan58 #817667 07/27/20 5:47 pm
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Originally Posted by koan58
If you were to blank off the small holes and install an oil seal, you would have to provide an alternative crankcase breather. One I think may be the best uses the front engine mount chamber. Holes are drilled through to the crankcase and a reed valve plumbed in the top.
Others have installed a vent on the timing cover, next to the inlet cam.

Either of these is possibly more trouble than you want to go to. As said, the T140 system works fine.

The front engine mount breather modification is the one I am considering. I still haven’t made up my mind, but I need to make the modifications in the next day or so before I close up the case if I’m going to do it. My biggest obstacle at the moment is finding a triplex primary sprocket that is machined to ride on the seal. If I can’t find one I’d have to modify my current sprocket.


Originally Posted by koan58
With my pre-unit 650 I am content to put up with the original timed breather and the minor sweating when used at sustained high rpm (which only happens on a motorway, say constant 4500+ rpm for hours) in exchange for the independence of the chaincase in terms of oil type and level (for best clutch performance).

Separating the primary oil from the engine oil was my main motivator behind looking into this. I still haven’t decided what I want to do.

Thanks guys, keep the suggestions coming!

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Originally Posted by koan58
Thrasher +1
The timed breather even struggles with a 650 at sustained high rpm

I know that only too well!

I only specified the 750 to avoid the usual arguments.


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I have to know, do you guys really run your 650s at 4500 rpm for hours on end, and regularly shift at 7000, or are these "fish stories"? If the former, my second question is: "Why?"

(Sorry for getting off-topic, but I've wondered about this all too often.)


Mark Z

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Mark Z #817796 07/28/20 5:22 pm
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Originally Posted by Mark Z
do you guys really run your 650s at 4500 rpm for hours on end...?

What do you do on a big road, where everyone is doing 70 mph or more?


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Hi Mondster, Here’s a few thoughts from my experience. That it as that.

In practice you will find no advantage to the front vent.

On paper front vent can give lower crankcase pressure resulting in more power due to pistons don’t displace as much air on the down stroke. Timed cam disc or reed valve allows this to happen. Small gains on the track give mor wins.

In practice the primary vent works quite well. The only down side was condensation in primary from continual short trip use. This is not problem for most these days.

I would recommend leave vent stock.

Yes this motors can run 4500 long distance but lower the tend to last longer.

Taking to 7000 often is very hard on motor. Guys that do it often see short motor life.

I run motor 4200 hour after hour. But when 100f+ I’ll back off to like 62 mph. Closer to 3900 ish. I go to 5000 often. 6000 on occasion. 7000 I avoid. No reason for me to spin that high.

Use dedicated break in oil & high zinc motor oil after break in.
Most of use use Mobil1 v-twin 20-50. Has provided very good wear & heat resistance. Tracking valve adjuster screw wear has doubled life. Clutch loves this oil.

I’ve covered 35610 miles from new. Original bores, pistons, rings, valve guides, cams, bearings etc. I feel oil is partly why.
Don


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Originally Posted by TR7RVMan
Most of use use Mobil1 v-twin 20-50.

Most of who?


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“I have to know, do you guys really run your 650s at 4500 rpm for hours on end, and regularly shift at 7000”

In my case it doesn’t happen very often, as I live on the Isle of Wight, which has no motorways at all, and only one stretch of dual-carriageway where the speed limit is 70mph for about a third of a mile.
The best stretch for a mad Sunday burn-up is a spectacular ~8.5 mile stretch of southwest coast road called the Military Road (60 mph legal limit) where even a bike like mine can be at 90-100+mph for many parts of it, though you’re taking great risks with your life and licence especially in tourist season. In the late 70’s I witnessed a manic race between a Kawa H2 and a BMW R90S, viewing from the high Blackgang Viewpoint (from where I could see the first half of the crazy competition) with trailing smokescreen! They were clearly maxing out, must have been doing much more than 100 mph for much of it.

Most of my enjoyment tends to be on more moderate 50-80 mph stretches with curves (it is a Triton).

On the occasions when I visit mainland England, I do generally run at 70 mph (~4100 rpm) on the motorways (otherwise you tend to suffer in the lorry lane) and if I have a deadline (for a ferry say) will sometimes up it to 80 mph (~4700 rpm).
It is at these rpm sustained for 1-2 hours that the engine sweats, whereas having fun on the island it doesn’t sweat at all.

I’m doubtful that I’ve ever taken it to 7000 rpm in the 40 years of ownership, it just doesn’t need it in the lower gears as there’s plenty of torque from below 3000 rpm, masses from 4000 rpm. 7000 rpm would be about 120 mph in top, I’ve not done more than approaching 110 mph a few times, absolute top speed is not what the bike (or me) is about.

What the bike (it’s much lighter than a standard Bonneville at about 340 lbs and I’m a bit more than half that) is good at is challenging much more modern (my engine and frame date from the late 50’s) bikes round the local bumpy and bendy roads. Other than on that stretch I described, my mates’ GPZ900 and Le Mans Mk3 struggle. More is not always better.

Mark Z #817832 07/28/20 9:09 pm
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Originally Posted by Mark Z
I have to know, do you guys really run your 650s at 4500 rpm for hours on end, and regularly shift at 7000, or are these "fish stories"? If the former, my second question is: "Why?"

(Sorry for getting off-topic, but I've wondered about this all too often.)

I can only speak for myself, but yes I ride all my bikes hard and the Triumph is no exception. Hopefully I'll be able to complete some brake and suspension improvements this winter that will allow it to be run even harder.

As far as your second question goes, why not? I enjoy using what I have, not preserving it for someone else.

Mark Z #817834 07/28/20 9:35 pm
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Originally Posted by Mark Z
I have to know, do you guys really run your 650s at 4500 rpm for hours on end, and regularly shift at 7000, or are these "fish stories"? If the former, my second question is: "Why?"

(Sorry for getting off-topic, but I've wondered about this all too often.)
Well, not hours on end but short intense rides of about an hour see my T140 around 5000 rpm about half the time in the lower gears and indicated 7000 rpm thriugh the gears maybe 10 times or so...I'm 73 ,and hopefully wear out this lump to a smoking nub and get my money's worth...
A guy here, Tigernuts ,claims to tour Europe for hours on end with a T140 at 80 mph and passes other vehicles at 100 mph...


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koan58 #817855 07/28/20 11:48 pm
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Originally Posted by koan58
“I have to know, do you guys really run your 650s at 4500 rpm for hours on end, and regularly shift at 7000”


lol

when i geared my T120 to 21/47, 4500 was only 77 mph, and that is marginally able to keep up with traffic on my local four lanes. i routinely ran around 5000, which is somewhere around 85. not for all that long, just to get the 20 miles to town. i would run that rpm in the lower gears, though, all the time. i don't shift all that high, because i'm more interested in speed than accelleration. but i'll shift at 6000 or so pretty regularly.

right now that same machine is geared 19/47, 4500 is only 70 mph. that's fine for the two lanes but not for the interstate. even on the two lanes its really buzzy. 60 mph is all its happy with, really.

i'll put the 21 back next time i have it apart. i'm 64, and i intend to die happy.


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My A65 had been modified with an added breather out the front of the primary. Most BSA I've seen with a primary breather add the tube at the back, I don't know what was in the mind of PO to put the tube out the front. He drilled three small holes into the crankcase, but left the crank oil seal in place. I have since removed the seal and routed the breather tube through a Mike's XS reed valve. Seems to work well, though the reed needs periodic cleaning. The thing with the BSA is that it's more prone to wet sumping, which can also overfill the primary.
My T120V breathes through the primary as standard. I used to have a big tube running up the rear fender, but have since mounted a filter directly to the exit pipe on the case.
Both of these share oil between engine and primary. Using a dedicated motorcycle oil and the clutch works well.
My Trident breathes as stock with the tube running into the back of the air cleaner. With a dry clutch oil is not an issue, so this bike gets VR1.
My twins rarely see the interstate. I tend to shift at 5-6000rpm and spend most time running about 4000.
On the other hand, the Trident doesn't come alive until 4500. It is more than happy to spend all day at 5000, and I don't shift until the high side of 6000. It revs freely to 7500.


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Rev counters? Pah! Proper Brit bikers don't need rev counters to know when to change gear, the engine tells you.

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Hi Tritonthrasher, Sorry. Should have made it clear. I mean the guys I ride with in my area. It is very popular in mid California. Gets hot in summer.
Don


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1985 I fitted a QPD belt drive to my T140D. As it had to run dry I fitted the crank seal and blocked off the 3 holes. I then used the TDC hole to fit my breather. This was all as recommended.

I had no end of trouble with oil mist ranging from very fine, to a fog (depending on revs/speed) and anyone sitting behind me got covered in oil. I tried a number of things including trying to fabricate a coffer dam set up in the hose to no avail. I eventually went back to chain and original breathing and my troubles stopped

















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Originally Posted by jimmymckenna
1985 I fitted a QPD belt drive to my T140D. As it had to run dry I fitted the crank seal and blocked off the 3 holes. I then used the TDC hole to fit my breather. This was all as recommended.

I had no end of trouble with oil mist ranging from very fine, to a fog (depending on revs/speed) and anyone sitting behind me got covered in oil. I tried a number of things including trying to fabricate a coffer dam set up in the hose to no avail. I eventually went back to chain and original breathing and my troubles stopped

I have to say the timing hole behind the barrel looks like a bad place to put a breather.


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Originally Posted by TR7RVMan
Hi Tritonthrasher, Sorry. Should have made it clear. I mean the guys I ride with in my area. It is very popular in mid California. Gets hot in summer.
Don

I’d probably have tried it myself if they sold it in the U.K.


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Originally Posted by triton thrasher
Originally Posted by Mark Z
do you guys really run your 650s at 4500 rpm for hours on end...?

What do you do on a big road, where everyone is doing 70 mph or more?

...A more considerate reply than I expected, TT! For the most part, I stay off the big roads. There is one highway, between here and my place of employment, which I will take if I'm in a hurry, and I'll do 70 mph, which on my A65 is 4100 rpm. But that's only 15 miles, and I'm not doing "4500+ rpm for hours". For more leisurely riding, there are plenty of secondary highways and even smaller roads around here to take me wherever I want to go.

I find my A65 runs best in the 3500 to 4000 rpm range, smoothly and with plenty of throttle response. This is about 3/8 throttle with my 32mm Miks, and the bike will run all day like that without breathing hard. It will pull easily from 40 mph in 4th gear if I'm not climbing a grade, without lugging or pinking. The only time I've ever had the bike over 70 or over 1/2 throttle at speed is when I was testing for main jet size. And the engine has never seen 7000 rpm in its lifetime. But the opinion has been expressed many times on the forum that it's not good to run an A65 that slowly, which led me to wonder if there's something different about my A65, or if it's simply a matter of preference. If it's the latter, I guess I'm content to merely "bimble about".


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Semper is a good example of when he rode to the north cal rally on his OIF in 2014, but likewise I have ridden for several hours with the engine buzzing along at 70-75 mph, with the gearing on my bike revs are slightly less at 3900 ish (19:42 gearing with the bob Newby clutch) the bike is fine on it, this is covering probably 100 miles before stopping for fuel/food or an ass rest break.


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Allan G #818001 07/30/20 12:38 am
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Originally Posted by Allan G
...with the engine buzzing along at 70-75 mph, with the gearing on my bike revs are slightly less at 3900 ish (19:42 gearing with the bob Newby clutch)

Well there you go Allan, with that gearing we're in the same ballpark as far as rpms go.


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I've been tempted to try a 47 tooth on the Trident to keep the revs down.
Nah, that would never work, I'd just go faster. laugh


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Originally Posted by DavidP
I've been tempted to try a 47 tooth on the Trident to keep the revs down.
Nah, that would never work, I'd just go faster. laugh
Try a Nova kit and 3600rpm at 60mph......but it has a sweet spot at 75 mph smile

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