Don Terrill’s Speed-Talk

There's a company in the UK that does a bearing conversion to get rid of the bushing used on the crankshaft on one side of the BSA twins. Other then this one down side to its design. Whats wrong with the BSA that they never seemed to be used in racing as much or competitive to the triumphs. Would l...

Little Mouse wrote:Just curious what company makes the billet triumph cranks and do they do other old engines.

Nourish in the UK makes Triumph billet cranks and maybe other old Brit Bikes. MAP in the USA makes a variety of billet cranks for Triumph and one for Norton's.

Yes, he did. Right, but have you tried using NOS cranks, i.e. cranks that are brand new -- never been used, been sitting on a shelf, with the short rods? If so do they last longer? This has been going on for many years even when NOS cranks could actually be bought .They are extremely rare and expen...

Yes, he did. I suspect that if you started out with the short rod 40 years ago the life expectancy of the crank would be the same as with the long rod. A different pattern of fatigue would be imparted to the part. Sure, you could improve the design to help eliminate the weaknesses but that is a dif...

cjperformance wrote:? In your 1st post you said the short rod is more likely to break cranks?

Thanks for noticing,a mistake, it's been corrected...

What about comp ratio, cam, timing curve differences between the 2 combos? Seeing you say they both use the same piston, that puts the short rod combo' s piston skirt closer to the crank's c/line ABDC. So how about bore length, obviously the skirt is further down the bore with the short rod in this...

where do the cranks break? We used to find plenty of Norton twin cranks with cracks in the drive end main journal. The fillet there is tiny, and more so when considering the nice radius on the rod journals. http://static.mijnwebwinkel.nl/winkel/obsoletebikeparts/full22307231_a.jpg Looks like Triump...

The pistons are not usually coated.. This is a race situation at power levels of 1.5 HP/ cubic inch ... The shorter rods must be a hair too much. This isn't my engine's problem but tuners of Triumphs talk about, but no reason is given. Then they get an expensive billet crank...I'm curious about the ...

BOOT wrote:They use the same piston?

Yes...

If it was a V8 car then just drop in a SBC. I have no experience with cars but 70's trucks the 6 and V-8 frame mounts are in a different location on the frame...At least that's what i remember...

What would be the factors causing more crankshaft breakage with a short rod? The situation is vintage Triumph bike engines. There's two ways to do a 750 cc engine. One uses the normal cylinder height with a 3.23 stroke and a 6.5 inch rod. The other is a 1/2 inch shorter cylinder,same 3.23 stroke and...

Our daughter accidentally filled the tank of her 90's Ford gas engine PU with Diesel. It pinged and rattled and stalled out. Drained the Diesel and filled it with gas....still pinged some until the next fill up. She drove the truck a few more years and it ran ok...

So..liners can be installed in bronze guides? I work on old Brit bikes ,usually have bronze guides . Removing guides can sometimes be an issue if it's a replacement guide in the pastthat was sized to big and "forced" into the guide bore broaching the bore. So if you remove the guide the bo...

I run a 650 cc OHV twin cylinder bike in land speed racing. I tried all the formulas concerning pipe length and exhaust length. Then spent a lot of time on the chassis dyno messing with this stuff. In the long run my bike makes best peak HP and the widest torque spread with the carbs fairly close to...

I race vintage 4 stroke British bikes. Reversion is common and said to be, in simple terms, the exhaust pulses coming back upstream pushing the intake mixture out the carb and then sucked back in on the next intake event, making the mixture excessively rich causing a severe bog at lower RPM's. For m...