Restoring & Modifying 1971 OIF TR120

[speedrattle]

another cause for too much oil in the sump is if tbe pickup tube falls out. i had one do that. the end is normally less than inch from the bottom of the crankcase, but if it falls out the level goes way up and the oil coming out the breather gets dramatic.

grab the tube and wiggle it to see if its loose. i sealed mine back in by giving it a tiny tap with a hammer to tighten the fit and then using red --not blue-- loctite. its been fine ever since

 

[NM Bonny]

another cause for too much oil in the sump is if tbe pickup tube falls out. i had one do that. the end is normally less than inch from the bottom of the crankcase, but if it falls out the level goes way up and the oil coming out the breather gets dramatic.

grab the tube and wiggle it to see if its loose. i sealed mine back in by giving it a tiny tap with a hammer to tighten the fit and then using red --not blue-- loctite. its been fine ever since

Wait... can this be done through the drain hole? I will be draining the sump and primary to inspect the latter and fit the 3-phase alternator.

 

[speedrattle]

yes. easily. the clues as to what is wrong are obvious

they dont fall out often but when the do you can wrap a pin punch in some masking tape and tap them back in through the drain. one of the few places i use red loctite.

just somethi g to check. takes about five minutes. clean that drain plug spotless before you take it out. its an unnecessary source of grit on the plug threads or even inside.

 

[NM Bonny]

yes. easily. the clues as to what is wrong are obvious

they dont fall out often but when the do you can wrap a pin punch in some masking tape and tap them back in through the drain. one of the few places i use red loctite.

just somethi g to check. takes about five minutes. clean that drain plug spotless before you take it out. its an unnecessary source of grit on the plug threads or even inside.

Okay, got it - thanks for the clarification and photos!

 

[NM Bonny]

Mmmm... showed up nice and oily!

 

[NM Bonny]

Aha - here we go. I knew that I'd seen this done! So, here are some photos of a Spaniard's '72 OIF Bonny with old-style, threaded intake ports like my bike--and running those finned aluminum manifold spacers discussed above, or something very similar.

It looks like maybe he just installed longer manifold studs in place of the OEM length versions to accommodate the finned spacers...?

Now, he has simply eliminated the OEM airbox, whereas I bent up custom side covers--but they curve back directly from the oil tank's flanges. So, if I were to get the measurements from the UK vendor with whom I corresponded briefly, presumably I could figure out whether my existing shorty K&Ns would clear with the added length.

P.S. - Kevin, it looks like he's got rearsets kind of like you had described, too...?

 

[Rudie]

photos of a Spaniard's '72 OIF Bonny with old-style, threaded intake ports like my bike--and running those finned aluminum manifold spacers discussed above, or something very similar.

It looks like maybe he just installed longer manifold studs in place of the OEM length versions to accommodate the finned spacers...?

if I were to get the measurements from the UK vendor with whom I corresponded briefly, presumably I could figure out whether my existing shorty K&Ns would clear with the added length.

rearsets

Mmmm ... not sure I would be happy with the looks of the gear lever ... any photos of the drive side showing that footrest and the rear brake linkage?

Btw, on the subject of final drive gearing, would you be happy replacing the complete conical hub rear wheel with one originally fitted either to a 71-74 T100 or any pre 71 twin? Reason I ask is that hub can have as little as 43 teeth and, if you are prepared to put up with teeth cast on the drum, you can have a q.d. hub. To answer your "does it fit" question, yes.

 

[NM Bonny]

Mmmm ... not sure I would be happy with the looks of the gear lever ... any photos of the drive side showing that footrest and the rear brake linkage?

Btw, on the subject of final drive gearing, would you be happy replacing the complete conical hub rear wheel with one originally fitted either to a 71-74 T100 or any pre 71 twin? Reason I ask is that hub can have as little as 43 teeth and, if you are prepared to put up with teeth cast on the drum, you can have a q.d. hub. To answer your "does it fit" question, yes.

On the carb spacers, I'm not sure how he fit them without contacting the petcocks, per the first photo. They're 1" thick per the website in the UK. No issue with the air cleaner clearing the side cover per the second photo.

Maybe he shoved his tank back an inch or so...? Mine is (I think) centered over the hold-down bolt but perhaps I'm remembering incorrectly, and there's a little room for fore-aft movement by sliding the bolt's head a bit...?

Here's the L/H side of his bike, re: your question about the brake rod setup.

On the final drive ratio, I rather like the conical hubs aesthetically and would prefer to keep the rear one (the front will only get ditched if, as we've discussed, I'm horrified at the braking force and want to go ahead with the DIY 11.5" front disc conversion).

Is it possible to purchase rear chain rings for the conical hubs with fewer teeth than 47? Would #37-1499 from the '70 bikes work? It's 46 teeth. If not, is it the I.D.? If that's the issue--and not bolt hole spacing--I wonder if I could turn it a bit without getting too close to the bolt holes.

 

[Rudie]

L/H side of his bike, re: your question about the brake rod setup.

Any reason posted for the master cylinder? Just curious.

Is it possible to purchase rear chain rings for the conical hubs with fewer teeth than 47?

Regret I do not know one way or the other. My feeling is it would certainly be difficult, because fewer teeth = smaller diameter, brings the chain closer to the mounting bolts? Socket cap mounting bolts would give a little more clearance to the chain but you might be into having the sprocket made specially?

Would #37-1499 from the '70 bikes work?

Again, I do not know for certain, but here I suspect not - while 70 twins and triples had 46 teeth, earlier twins had been fitted with 43 teeth sprockets on the same brake drum, that suggests the mounting is different?

 

[NM Bonny]

Any reason posted for the master cylinder? Just curious.

Sorry, I don't understand. What master cylinder are you referring to?

 

[NM Bonny]

Regret I do not know one way or the other. My feeling is it would certainly be difficult, because fewer teeth = smaller diameter, brings the chain closer to the mounting bolts? Socket cap mounting bolts would give a little more clearance to the chain but you might be into having the sprocket made specially?


Again, I do not know for certain, but here I suspect not - while 70 twins and triples had 46 teeth, earlier twins had been fitted with 43 teeth sprockets on the same brake drum, that suggests the mounting is different?

Okay, thanks. I've asked the vendor who sold me a 46-tooth ring whether that was an error (I had told them I had a '71 OIF Bonneville), or if it will indeed fit the conical hub. If they tell me it won't but don't clarify why not, I'll pull the rear wheel and lay the two rings over each other to compare mounting bolt holes and central bore I.D., and post the results.

As discussed earlier, if it's merely a matter of opening up the central bore I.D., I can have my neighbor/machinist do that (actually, his son and foreman; my friend died last weekend of liver cancer to my great dismay). Alternatively, one can open up such a bore with reasonable accuracy using a Dremel, believe it or not, as discussed here in the instructions for my DIY rear disc brake conversion for Spridgets.

You don't need much material at the inboard (in a radial dimension) edge of those mounting bolt holes, as the force exerted on the thick steel at those points--and on the bolts--is shear or perpendicular to the bolts' long axes, and especially with such a large span between the bolts, together with the ring's central bore resting on the flange in the hub, there's virtually no chance of tear-out from the ring shifting vis-a-vis its axis from torque exerted by the chain.

So, if there's a fitment issue, let's hope it's the central bore, and that there's room to enlarge it slightly!

In fact does anyone have a 46-tooth #37-1499 chainring handy to measure the central bore? That'd facilitate a quick and easy comparison with the part I have on the bench. Also, it'd help to take two other measurements: (i) between two adjacent bolt holes; and (ii) between any two holes across the central bore (indicating which two were chosen).

 

[Rudie]

What master cylinder are you referring to?

View attachment 56937
My mistake - the photo becomes blurred when enlarged, I realise it is the standard brake light switch and the bolt that presses on the switch's central button.

 

[NM Bonny]

So, Kyle Jones of KM Jones, the OIF parts specialist website, says: "You need a 5 bolt hole sprocket, so the one you bought won't work."

Didn't notice that the number of bolt holes was different. He's happy to swap it out for the OIF-specific part.

However, I've asked him whether the I.D. of the central bore matches up, because if it does--or it it's close enough that I can safely enlarge it per the above post--I'll just re-drill the 46-tooth ring for the OIF ring's bolt holes. Simple operation with a drill press.

That'd be really cool because it'd lower the rpms at speed a bit more. Together with the 20-tooth front sprocket I've got (and which evidently will fit my machine), I'd be curious to see what revs I net at 65 and 70 mph.

 

[speedrattle]

ive got 43 sprocket/drum and 46 ring sprockets sitting around. for the life of me i cant find the box with my 5-speed stuff, so i dont have a 47 conical to measure. ill put a tape on the 4-speed pieces tonight.

you want to know what 20/47 will get you in rpm at 65 and 70? you have a stock 4.00-18 wheel with a normal tire? ill calculate that out. i have a spreadsheet i wrote for gear ratios that does that ascfast as you can type.

you can fit a 20 with no modifications, and a 21 if you notch the trapdoor. some aftermarket 20s have taller teeth and wont go through, but ive only seen that once.

 

[speedrattle]

a 650 triumph with 20/47 gearing and a 4.00-18 rear wheel going 60.3 mph will be turning 3675 rpm.

64.8 mph---3950 rpm

70.1 mph ---4275 rpm

at 6800 it will be going 111.5 mph.

this assumes your tire has a circumference of 81.4 inches. to measure that, mark the tire where it contacts the floor, then sit on the bike and roll it forward until the mark goes around and sits on the floor again. mark the floor and measure between the marks.

 

[NM Bonny]

a 650 triumph with 20/47 gearing and a 4.00-18 rear wheel going 60.3 mph will be turning 3675 rpm.

64.8 mph---3950 rpm

70.1 mph ---4275 rpm

at 6800 it will be going 111.5 mph.

this assumes your tire has a circumference of 81.4 inches. to measure that, mark the tire where it contacts the floor, then sit on the bike and roll it forward until the mark goes around and sits on the floor again. mark the floor and measure between the marks.

Okay - thanks for doing this. The 4.00-18 Bridgestone Battlax I bought for the rear is 81.25", measured with a string--but that's unmounted and un-inflated. Close to the figure you're using, if a little smaller--though I don't know if inflating it will make any difference...? It's a pretty beefy casing.

I was thinking that these babies are really turning at highway speeds, but then I remembered that the 1974 Honda 550 I owned years ago (a SOHC engine, of course) turned around 4,900 at 60 mph, and 5,700 at 70. So, these pushrod engines are actually kind of loping along at speed...

I heard back from KM Jones Enterprises, and the owner said:

"The inner diameter of the sprocket you bought [37-1499] is smaller than 37-3747, the sprocket that normally would have come on your bike. You could try drilling new holes, but you're going to be getting close to the teeth of the sprocket, and I don't know with a smaller inner diameter if it will fit properly on your hub, I've never tried doing that before."

So, although it sounds like I'm probably out of luck--and the bolt holes getting close to the chain are the issue--what I'll do is put the bike up on the stand, pull the rear wheel, remove the chain ring, and overlay it with the 46-tooth sprocket.

I was waiting to work on the rear end until my swing-arm bushing removal tool arrived (back ordered), but I'd like to rule this out or it'll keep distracting me until I do. The bits for the front-end work have all arrived, so I'm just waiting for the bitter cold to ease up to get out in the garage and get cracking.

 

[NM Bonny]

BTW - those watching this build may be interested in a thread I started about a vintage tour. It would be really neat to continue tracing the route per my suggested method of accommodating the participants.

 

[NM Bonny]

Ran across this '73 T140 and leaving aside the Trackman frame, there are certain aspects similar to how I'm envisioning this build.

For one thing, I really like the head pipes. I am not crazy about the usual racer style that sweep back sharply across the primary and timing covers--yet these are tucked in for cornering clearance. Anyone recognize the maker or vendor?

 

[Rudie]

head pipes. I am not crazy about the usual racer style that sweep back sharply across the primary and timing covers--yet these are tucked in for cornering clearance.

Afaik, pipes across the primary and timing covers were first created in the UK in the late 1950s or early 1960s by racers as tyre compounds improved, so the lower front bend in standard pipes did not ground under a combination of hard braking and cornering? Later copied by "cafe racers".

The pipes in the photos appear to be based on US style "TT pipes", although they are not as close together under the engine as TT pipes usually are?

The pipes in the photos, the lower front bend could still ground? Or maybe you will not brake/corner that hard?

 

[NM Bonny]

Afaik, pipes across the primary and timing covers were first created in the UK in the late 1950s or early 1960s by racers as tyre compounds improved, so the lower front bend in standard pipes did not ground under a combination of hard braking and cornering? Later copied by "cafe racers".

The pipes in the photos appear to be based on US style "TT pipes", although they are not as close together under the engine as TT pipes usually are?

The pipes in the photos, the lower front bend could still ground? Or maybe you will not brake/corner that hard?

Well, good point re: the TT pipes--and now that I look closely at the second photo showing the underside of the bike, they'd come close to interfering with R&R of my OIF reservoir cover (I have installed the aluminum plate with integral paper filter).

Also, per this photo, they'd interfere with the adapter I welded up to use my floor jack with this bike.

Guess I should stay with the stock style pipes. I suppose it is unlikely I'll be riding as aggressively as I used to, when grounding foot pegs and mufflers was actually an issue...