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Ok Folks,

I have completed welding up a engine work stand for my 71' T120R and im ready to begin rebuilding.

I would like some tips what to look for, or look at, for a motor that i have very limited history of, cept for the fact i own it.

Note: when the motor was in the bike it had compression but seemed to make an interesting rattle when kicked. I never has the motor running as the wiring was all over the place and missing coils etc. Also the gear selector seems to be stuck and you cant feel it click into other gears.

Also if the tips could be put in order of what to do first would be great.



I don't ask for much do i??

Cheers fella's



[ This message was edited by: valiantbultaco on 2006-12-09 20:37 ]
 

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Get your shop manual and proceed from step "A" to step "Z".

If the engine is already out, already going to be dismantled and you are learning from "square 1", may as well be thorough.

There are no unimportant details, except maybe the..... Never mind; there are no unimportant details!
 

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Crankshaft.....CLEAN the slugde trap. Clean enough to eat from. You have to remove the plug and the flywheel bolt which locates the stamped steel tube inside. Then pull the tube out and clean it and the inside of the crankshaft. Clean the drill way from the crank right side end all the way to the sludge trap. Clean, and then clean again. Clean the holes in the journals. Reassemble and use red loctite on the flywheel bolt and torque to 33 foot pounds. Install the plug and stake the threads with a center punch to keep the plug in place. Use a hex socket plug if you want to be able to easily remove the plug later. Polish the journals before doing the final cleaning and assembly. Measure everything....and check the alternator keyway for damage. Make sure nobody has beaten on the end of the crank to remove it and caused it to mushroom. If so, have it turned back to size.

Rods.....Check the big ends for ovality and resize, if out of round, or get different rods. Replace the small end bushes and have them pin fitted. Sand out all the nicks in the alloy and polish to a high luster.

Crankcases..... Use a drill bit that will just fit inside the blind holes of the cover screws and ream out the holes by hand. You may find sealer impacted up inside these holes and you have to get it out. Use Carb cleaner in the spray can and the little red tube to get back to the end of the hole and blast the stuff out. Use a tap to clean up the threads (1/4 X 20). Blow across the tops of the holes with compressed air to get them clean and dry. Use stainless allens in place of the stock screws.
This will save you a lot of grief....have the case machined to accept the plunger-type shift detent, as used on all Triumph big twins EXCEPT the late 70s to 72s. The factory tried to save a few shillings and bolloxed it up for a few years by fitting a leaf spring on the inner gearbox cover. Remove this and discard. The boss is still there under the gearbox casting, and it can be bored out, threaded and you can install a detent from and earlier 650. This may also do something to fix your shifting problem. Borrowing an earlier case to show the machinist will save a lot of hassle in communicating what you want.
Fit all new bearings and install them in a hot case while the bearings are ice cold. If you fit new cam bushes, they will need to be fitted to your cams and line reamed. Don't forget to drill the oil feeds, and use the hard bronze ones available from Kibblewhite...not stock replacement oilite bushes.
Make sure the studs are all in and tight....double nut them and cinch them. Clean all gasket surfaces. If the cam idler pinion shaft is loose in its boss, clean with brake cleaner and install with loctite red or stud and bearing mount green. The center hole faces outward, and the small cross drill hole goes downward. If there is any noticable wear, replace with new.

Oil pump.....test it in a bowl of oil by operating the plungers...you should get a strong blast of oil out of the ports. If not, remove the square head caps on the bottom, remove the springs and check balls and clean. Then put the balls back in and using a small pin punch, lightly tap them into the brass pump body to seat the ball, install new springs and the caps.
I would fit an oval port pump from a late 73-on 750 twin, as they move more oil.

Cams....the 71s have good nitride hardened cams, so make sure there isn't any facetting on the lobes or wear on the journals and refit them. Regrind the tappets so that you have new wear faces to engage the cam lobes. If you want to soften the cam timing and make the bike a little more tractable, you can fit STD (0.750" radius) tappets in place of the R (1.250" radius) tappets, reducing wear and tear on the valve train and yielding a torque band that starts earlier and gives better mid range punch, with a little less top end hp. If you want that top end Bonneville rush, keep the R tappets. Drill out the oil drain holes in the tappet blocks to improve oil draining and to allow the top end to communicate with the crankcase breather more effectively.
Make sure the small pin in the right end of the exhaust cam is in place, this locates the auto advance of the points system so that it is much easier to get the initial ignition timing correct.

Cylinder.....I like big bore kits. With any piston, make sure the pistons fit well and the rings fit in the ring grooves...I would use new pistons, if there is any doubt. And since you will have new pistons, get them in the next oversize and have the cylinders bored and honed to fit. Fit the ring end gaps so that there is at least 14 thou on the top ring and at least 12 thou on the other two rings. I set the gaps of the two compression rings at 180 apart from each other and the oil ring gap at 90 degrees to that line. I position the left cylinder top gap at the 7 oclock position, the second ring at the 1 oclock position and the oil ring gap at the four oclock position. And mirror image for the right side. Then, after you have done all the machine work and cleaning, all the fitting an choosing, have the crank, rods, rod bearings, piston assemblies balanced at the machine shop. I use 78%, the factory used 85%.
When assembling the pistons to the rods after getting the cases bolted up, use a shaped piece of thin metal, plywood, or plastic to support the piston skirts on top of the studs. With the piston in hand, put the inboard clips in the pistons, then put the pistons on the rods and push the pins into place. Warming the pistons will make this easier. Then, with clean rags stuffed in the case to catch any dropped items, install the outboard clips. Make absolutely certain that all the clips are seated in their grooves.

Head.....I prophylactically install one piece steel spark plug inserts (NOT helicoils) to eliminate the chance of a stripped head while doing maintenance. Using an extra long bit, I drill an angled drain hole next to the plug hole to allow water and crud to drain out of the otherwise blind hole. Check the head surfaces for flatness and lap as necessary. Clean the blind holes for the rocker box bolts as per the cover screw holes. Use new valve springs, whether stock or high performance, and check the packed length to be sure that you have enough spring tension to control the valves and not so much that you break something. I use the MAP Ampco 45 guides and Kibblewhite Black Diamond valves, which are available in oversize if your seats are deep in the head from inexpert valve grinding or too many top end overhauls. These are so much better than any valve I have ever used, that I don't use anything else. Same with the guides.
I use a lightened valve train...from tappets to valve spring retainers, to minimize the wear and tear on the valve train, especially the camshafts....which are only accessible by complete disassembly of the engine. So, get the cams and crank right the first time!! A light valve train also means that less spring pressure can be used and still have valve control at high rpm.
I use cam pinions from the five speed engines, the ones with the metric bearing in the right side of the case. They are heavier than the 650 four speed engine pinions. They act as a flywheel and damp the pulsations of the cam's operation and on the intake, the pulses induced by the oil pump.
Filing little lead-in ramps into the back of the keyways will make installation onto the keys much easier...I use a jewler's file. You don't need to remove much metal here....just about 5 thou will do. If the keys are loose in the cam keyways, then put them on a hard, solid surface (like an anvil or vise) with the flat side down and the curved side up, and tap them smartly with a hammer to swell the bottom slightly.

Gearbox.....new bushings, bearings, and thrust washers, followed by careful inspection and assembly, is about all you need here, as you have the best 4 speed gearset from Triumph. Be certain that the tapered end is not buggered up or that the keyway isn't woggled out. These need to be ***** near perfect if you want the clutch to remain in place. Install all new springs in the shifter pawls and housing. If the lifter button in the center of the clutch lifter mechanism is worn with a deep pit, change that. Use a new clutch rod and bush in the mainshaft end. Use a new kickstart ratchet spring and kicker return spring.

Primary....be sure the 3 small holes under the main bearing are open. Use a new primary chain and adjuster assembly....blade, rod, and nut. Check the alignment of the sprockets with a straightedge and adjust, if necessary, with shims under the engine sprocket. Adjust to 3/8" play total up to down with moderate force. Look for a crack outboard of the drain plug at the rear of the case...the wall is very thin here and frequently shows up with a crack that will yield an annoying leak.
Use a new set of plates....both friction and plain plates, or have the stock plain plates sandblasted with coarse garnet or equivalent....you have to have some significant tooth to have the clutch operate properly. I use MAP's clutch plates. Use a new thrust washer. Install new damper rubbers in the clutch center. Change the spring pins if the threads are damaged or if there is notching near the square head. New springs and nuts are also a good idea. MAP also makes an alloy pressure plate with a little ball bearing for the clutch rod. I use it, and it will make for a smoother clutch.
The alternator rotor must be a snug fit, requiring it to be tapped into place with a soft hammer....if it slides on, it's too loose and a danger to your crankshaft. Clean the crankshaft end and the rotor bore and use blue loctite to tighten it up, or even better, get a Sparx three phase alterator kit with the new rotor. I like the three phase alternators as you can run a serious headlight, and I figure more is better, too much is not enough.

Use all new seals, gaskets, and orings. Leave the timing access cover off of the primary cover so that you can strobe time the engine. Torque the head bolts to 10% over the recommended figure on initial assembly. Put them to specs on subsequent torquings. Adjust the valves to a slightly looser spec....like 4 and 6 thou....for the initial start up and readjust after the first retorquing. One or two retorques should do it, adjusting the valves every time.
Disassemble the points plate completely and clean and inspect. Replace any screws or eccentrics which are too buggered up to reuse and lightly grease the secondary plates and eccentrics with some silicone grease. Reassemble, and install new points after cleaning the contact faces with brake cleaner. I used 4BA allen screws in place of the slotted screws, however, they may be hard to come by, but if you can get them, it will make adjustments very easy. Disassemble the auto advance and clean and polish the pivots. Fit new springs and lightly grease the pivots, reassemble. It should work smoothly with no wobble.
There is more, but the caffeine is wearing off.
 

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I went through the same ordeal on a 67 back in the eighties. I got a Clymer manual and have been hooked since. Using Clymer manuals I have since went through three Triumph and one BSA motor. The book you need covers Triumph 1963 to 1979 500/750 twins, motors and trannys, frame wiring etc. and is designed to keep your work in the order it should be done. Once you make it to the sludge trap, it's a nice journey all the way to torquing the last bolt! Think of it as a full scale size model kit.

Edit: Move in next door to Mecchanica!

[ This message was edited by: red59 on 2006-12-10 19:00 ]
 

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Discussion Starter #5
yeah i think i will move next door to Mecchanica.

Ive always wanted a surrogate dad who lives in Hawaii.

I'd spend all my time surfing whilst Mecchanica would be playing with spanners. Good trade huh??
 

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I got a video put out by Cub Video I think. Hughie Hancox broke down and rebuilt a 1970 650 cc engine. He walked you thru it step by step. I had my laptop in the garage and paused the video after each step, and so on. It was a peice of cake.

I have no mechanical talent what soever :hammer: . Search for it. Somewhere around this forum I posted a link to it, but that was a long time ago.

PS found it:
Video

[ This message was edited by: quagmire on 2006-12-11 12:57 ]
 

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EEEEEK....the guy in the photo at the top of the linked page????? He could be my twin brother!!!!! Scary. I wonder if that's Dave Quinn? I've bought a lot of things from him.
Tell ya what.....Mario Perna from MAP could also be my brother....spooky, how much we look alike!!!!
 

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Discussion Starter #9
They say everyone's got a twin in this world. Sound like you have more?? I think ive seen that guy in another type of video......the man's got talent!!!

I'll bring the beer but none of that watery american stuff :wink:
 

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Right, I said BEER, not eagle piss. However, some of our microbrewery beer is pretty good, but very hoppy. So are Sam Adams' various brews.
As if living in Hawaii wasn't good enough, one of my friends is a brewmaster at a local micobrewery and seafood resturant.
 

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On 2006-12-12 12:14, Mecchanica wrote:
Right, I said BEER, not eagle piss. However, some of our microbrewery beer is pretty good, but very hoppy. So are Sam Adams' various brews.
As if living in Hawaii wasn't good enough, one of my friends is a brewmaster at a local micobrewery and seafood resturant.
WHAT A LIFE! MOTO,BEER,SEAFOOD!
 

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OH, here is a handy thing. If you don't want to weld up an engine stand, you can make a handy-dandy rig by using some short pieces of 1 X 8 s and making a magic box. Actually, a rectangle, as the top and bottom are open. Mine is about 9 X 12 inches and you can rest a lot of different engines in or on it so that they don't roll around on the bench and the crank end isn't digging into the bench. You can also notch two opposite sides to accomodate the crankshaft and that keeps it from rolling about and you can clamp the box to the bench for torqueing operations, or slip a fork tube on one crank end to hold it.

[ This message was edited by: Mecchanica on 2006-12-13 15:37 ]
 
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