Frank's Triumph 750 engine overhaul & resto-mod

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

I learned that there are no "early style" 75mm pistons available in ANY oversize (except the ones cast from melted diamonds mixed with gold)

The trick is to use "late style" 76mm.

76 STD = 75 + .040
76 + .020 = 75 + .060
76 + .040 = 75 + .080 (getting awfully thin between the bores, not recommended)

When Triumph first made 750s, they were really only 728cc. They promptly fixed that.

 

[Sea Dog]

Re: Triumph 750 engine overhaul start to finish

Fantastic documentation and workmanship GP. Always learn something from your work.

 

[DaveM]

Re: Triumph 750 engine overhaul start to finish

It sure is a COOL thread, thanks Paul

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Big day today; no, the cad plated stuff came and went while I was at the machine shop. Dang! Forgot about the C.O.D. and will have to be here tomorrow to receive it.

Cylinders came out great, will post a photo when I get them painted. Turns out I had left a spare set of 650 cylinders at the machine shop last year, so I will send the previous incorrect set of late 750 +.020 pistons back and have them send me a set of 650 +.040 pistons to match up the spare jugs. Kinda like Christmas in April.

Head looks good, it has some wear & tear, but nothing a good flame ring head gasket won't seal. Kibblewhite guides & Black Diamond valves went together with no issues.



I borrowed my friend Keith's spark plug Helicoil kit and got after both holes. Before...

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

I've done small helicoil repairs, this one is slightly different; the threading tap has the standard plug size then shanks up to the helicoil size-



Nice tapped hole-



One insert in place, a look at the other to see the teeth that the top threads "grab" with once you set them-

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Setting the top threads with the tapered setting tool-



Finished insert-



Nice clean combustion chamber end-

 

[CarlS]

Re: Triumph 750 engine overhaul start to finish

Very nice work!

 

[mikechev]

Re: Triumph 750 engine overhaul start to finish

Great photos!

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Cylinders got a thorough washing, then blast dry, mask & paint with Rust-O-Leum gloss black rattle can-



Next, clean out the guide block bores; I find this better than masking, just let them get what little overspray, then give 'em a quick pass with a small bore hone (bottom photo). Note hard, broken o-rings and new replacements-



Tried to employ my field-fabricated guide block tool that I made from a broken guide block (on the left, above) and two trashed cam followers, but I found I need to turn down the shoulder or it interferes with the cylinder fins. instead used a store-bought tool (nice). New copper washers and the jugs are all done.



STILL WAITING ON CAD PLATED HARDWARE! it's going to be a L O N G day...

 

[Rocky]

Re: Triumph 750 engine overhaul start to finish

Great stuff

 

[CarlS]

Re: Triumph 750 engine overhaul start to finish

Great pictorial documentation and great work.

 

[Sea Dog]

Re: Triumph 750 engine overhaul start to finish

Looking very nice.

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

cad plated hardware FINALLY arrived, but this engine will have to wait it's turn on the bench 'till i get the '83 back in it's chassis today or tomorrow.

 

[CarlS]

Re: Triumph 750 engine overhaul start to finish

Good to hear that you finally got the hardware.

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Pancho stopped by this afternoon to pick up his cad plated stuff and to drop off the powdercoated engine covers-



Nothing else today, but will be back on it next week.

 

[Sea Dog]

Re: Triumph 750 engine overhaul start to finish

Now that will stand out from the crowd

 

[CarlS]

Re: Triumph 750 engine overhaul start to finish

Those look really great!

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Back to work! Almost 3 months since the last time I uncovered this engine on the bench...

Rounded up tools from the last two projects I had been thrashing on, cleaned up my work area and got right in to installing the layshaft needle bearings and drive sprocket nut with locktab washer.

I used the layshaft to tap the needle bearing in place in the case half, as it was impractical to press it in place now. Tightening the drive sprocket nut was easy: just wrap a section of drive chain around the sprocket and clamp a pair of vice-grips to hold it steady, then ground about 1/4 of the last worm tooth on my large crescent wrench to allow it to open another 1/4"; held the large crescent at 90 degrees to the face of the nut and used a second crescent slipped over the heavy part of the bigger wrench to turn it with (I should have gotten a picture). Anyway, here it is, done-



Next, I installed the inner bronze bushing using a dab of grease-



Then, installed a new chain oiler tube and primary chain tensioner pad, and closed the clutch door with new gasket & seal-

.

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Now to the transmission. I'm getting better at installing and indexing 5-speed gear clusters; it's not hard if you work slowly "BY THE BOOK". I always print out the appropriate shop manual pages before I start in on an assembly. Gearbox installed with camplate in NEUTRAL position-



When installing the gearbox inner cover, you need to select FIRST GEAR by rotating the camplate, paste the bronze layshaft bushing in place with a swipe of grease, install the new gasket, and slip the inner cover in place stopping about 1/4" short of fully home. Then, simply index the top edge of the 2nd tooth from the bottom, aligning it with an imaginary line between the shifter shaft and the mainshaft-



New clutch rod bushing in place, retainer nut and new locktab washer in place on kicker gears. (2) inner fasteners installed- one phillips, one allen; that's how they come from the factory!

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Next, I installed the primary system; greased up the clutch hub rollers (all 20 of them)-



Then, installed the new Spark alternator rotor after dressing the crankshaft nose with emery cloth (they tend to be too tight of a fit) and shimmed the stator before tightening it all down-



Installed all new Emgo clutch friction plates and nipped up the freshly cad plated pressure plate assembly-



Transmission and primary system done, 3 hours flat.