Frank's Triumph 750 engine overhaul & resto-mod

[grandpaul]

I acquired a '73 TR7RV rolling project last year as partial payment on a client build, rounded up several of the missing parts and put it on e-bay. It turned out there was a very interested potential bidder from right here in Laredo, Texas; his name is Francisco "Pancho" and he has already built a very nice Honda cafe racer. We chatted a while and came to terms, then I loaded up my pickup and dropped the bike at his place. A while back, he brought me the forks for disassembly, and the engine for overhaul.

So, here we go with the overhaul.

"Before"

 

[grandpaul]

Re: Triumph 650 engine overhaul starft to finish

The engine was "frozen". At least there were no claims from the previous owner like "it was running when I parked it"...

Here's WHY it was frozen - water in the cylinders -

You can see the indented piston from beating on it with a sledge hammer...

 

[grandpaul]

Re: Triumph 650 engine overhaul starft to finish

It took quite a bit of beating on it to knock it loose, and I also lifted the cylinders and chocked them up with a couple of head bolts and sockets to get the last 2 inches out of the cylinders.

Note the head bolts screwed onto the front two cylinder base studs, sockets were used on the backside; it worked a treat...

The left piston loosened off after the first whack, the right piston fought me all the way out!

 

[grandpaul]

Re: Triumph 650 engine overhaul starft to finish

Pistons were trashed before I beat the flat top into the left one anyway.

Cylinders are standard overbore and I considered leaving them standard, but they did suffer mild scratching, so I played it safe and went with first oversize on the bores.

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

Timing chest didn't look too bad inside, just a bit of sludge & grunt.

...same with the tranny covers.

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

INSIDE the tranny was different. Definite rust patches that will need to be wire-wheeled. Note the roughed up mainshaft end and totally missing clutch rod bushing!

Underside of engine was REALLY filthy. Not sure how well you can tell it suffered a non-typical chain failure that blew out the BOTTOM of the case instead of the usual topside blowout. Chain must have snapped right at the point where the drive sprocket just got a hold of it, spitting the bitter end out the bottom.

Up to this point, no special tools were needed, unless you include the 5-pound sledge hammer on top of the piston, and the 10-pounder I was beating it with.

From here, all you typically need is the crank pinion puller, clutch hub puller, and engine sprocket puller.

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

Clutch pack was one solid frozen lump. A fair assumption is that the previous owner didn't know about un-sticking the plates, and the bike sat 'till it well and truly froze up.

Clutch hub is pretty rough, the spline grooves are rutted; it will be replaced.

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

Clutch hub came right off, and cases slid apart surprisingly easy. Both main bearings even slipped off the crank by hand (I'd rather they were a slight press fit, and the new ones will be Loctited if need be)

Not too bad inside the crankcase, average amount of crud...

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

Rather than drill two tiny pilot holes and use a pin punch to remove the drive side outer bearing race, I prefer to weld a bolt to the race and simply give it a tap while the cases are still too hot to touch.

The other two pix are just for reference for final insertion alignment of the layshaft needle bearing.

I didn't get a picture of it, but I heated the outer case with a torch and used a stray round-shaped part (of the proper size to just clear the cutout, and gain as much purchase on the roller faces as possible) to drift out the tranny mainshaft bearing; it took three easy taps to pop it right out. All the other tranny bearings dropped out with just heat; THAT'S the way I like it!

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

Ah, yes, the bloody SLUDGE TRAP!

Sometimes they're easy, sometimes they're hard, and once in a while they are an absolute PAIN IN THE BUTT. Guess which one I hit on this spin of the wheel?

RIGHT! Pain in the butt.

Had to weld a washer to the trap plug (weld bead on the washer's inner diameter), then weld a nut to the washer, then unscrew it like it should have unscrewed in the first place (I'm sure the heat soak from welding helped).

Sludge tube was almost completely plugged, only a thin tunnel through the sludge, and one of the 4 rod feed holes was plugged solid. Good thing something less serious happened to park the bike, before catastrophic crank/rod bearing failure.

The sludge tube was well and truly frozen in place with concreted metallic sludge, so removal involved destruction rather than an easy extraction with a large bolt.

So, the crank is sitting in the parts wash tub, flowing freely...

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

12 hours in the shop up to this point.

Overhaul will include:
Complete gasket set with seals, o-rings & flame ring composite head gasket
.020 oversize JCC pistons with Hepolite rings
NSK metric main bearings
Standard size rod bearing shells
Transmission bearings & bushings
Primary chain & adjuster slipper pad
All locktab washers
All rubber booties
Clutch centre cush pad set
Sludge tube w/ hex-head plug
Clutch friction plate set
Patent plate & 3 tap screws
Glass bead blasting on all cases, cylinder & head
.020 overbore of cylinders, and final honing to .0045 clearance on the new pistons
Valve lapping
Thorough acid wash of all parts after wire brushing all rust spots
Thorough hot wash to remove all residue
Complete Sparx electronics upgrade (ignition, alternator & regulator/rectifier w/ integrated capacitor for battery-less running)

Most of the new parts have already arrive, pix later...

 

[grandpaul]

Re: Triumph 650 engine overhaul start to finish

For no good reason, here is my cell phone picture of the plugged sludge trap.

 

[CarlS]

Re: Triumph 750 engine overhaul start to finish

Very good thread Paul. That sludge trap brought back memories! LOL

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

...and maybe a tear or two?

hee hee

 

[CarlS]

Re: Triumph 750 engine overhaul start to finish

Yes, that too!!! (laughing)

 

[FrankDaTank]

Re: Triumph 750 engine overhaul start to finish

Hello Paul,

I'm very excited to see progress, both on your end and in my garage. Thanks for doing a build tread on the engine!

Pancho

 

[DaveM]

Re: Triumph 750 engine overhaul start to finish

Wow this motor sure was in need of a bit of TLC

 

[grandpaul]

Re: Triumph 750 engine overhaul start to finish

Welcome, Pancho!

 

[CarlS]

Re: Triumph 750 engine overhaul start to finish

We love restoration threads here.

 

[keystiger]

Re: Triumph 750 engine overhaul start to finish

Woohoo great thread, can't wait to see the finished product.