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post #1 of 15 (permalink) Old 06-23-2019, 09:29 AM Thread Starter
Grand Prix 250
Main Motorcycle: 1979 T140E
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What would you recommend ??

I'm making plans to strip down my 1979 T140E engine for gasket replacement to cure the annoying oil leaks I am experiencing. The bike runs sweet with no lack of power and no smoke. I want to replace rocker cover gaskets, timing cover seals, cover gasket and ignition module grommet. Head gasket, push rod seals and O-rings, Cylinder block base gasket, Drive sprocket seal and all associated seals and gaskets on the primary side. In short, pretty much every seal and gasket short of crankshaft and gearbox removal. So I have a question for those experienced in OIF bikes, and a general question;
1) Can I do these repairs with the engine still in the frame? 2) Would you take the engine down this far without doing any machine work? Valve job, new rings, etc?? Am I asking for trouble if I do not ?
Thanks in advance for your input!
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post #2 of 15 (permalink) Old 06-23-2019, 10:39 AM
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Yes you can do all of the work listed with the engine still in the frame

leave the rear drive chain fitted until you have loosened the big nut that holds the drive sprocket - a standard sprocket will pass through the "inspection plate " hole into the primary - in addition to replacing the seal use sealant on the splines of the output shaft

if you are sure that all is OK with the engine then you can just rebuild as it stands - however i would recomend a cylinder head strip to check for loose guides - and for wear in the guides or valve stems - and if all OK a light lapping in the valve to seat faces

if it looks good leave it as it is - dont do unnecessary work just because its stripped down
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post #3 of 15 (permalink) Old 06-23-2019, 10:51 AM
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I agree with wol. I would probably put new rings in, but thatís me. If itís not smoking or using oil I wouldnít disagree with leaving the rings alone.
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post #4 of 15 (permalink) Old 06-23-2019, 05:23 PM
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My T120 started leaking oil last year from various gaskets. It burned very little oil but when replacing gaskets, i checked ring gap and they were very worn. replaced them and the gaskets and no leaks. I suspect you might have worn rings causing crankcase pressure to rise and pushing the oil out. For £30 spent on rings, i would change them.
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Now,where did that bit fall off ?
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post #5 of 15 (permalink) Old 06-23-2019, 07:00 PM
Grand Prix 500
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Originally Posted by rambo View Post
My T120 started leaking oil last year from various gaskets. It burned very little oil but when replacing gaskets, i checked ring gap and they were very worn. replaced them and the gaskets and no leaks. I suspect you might have worn rings causing crankcase pressure to rise and pushing the oil out. For £30 spent on rings, i would change them.
That's a good point.
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post #6 of 15 (permalink) Old 06-23-2019, 07:58 PM
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Originally Posted by wol View Post
leave the rear drive chain fitted until you have loosened the big nut that holds the drive sprocket - a standard sprocket will pass through the "inspection plate " hole into the primary - in addition to replacing the seal use sealant on the splines of the output shaft
in some forty-odd years of messing with these, i never ever take this nut off until after the chain is tossed and usually the engine is out and on the stand. and the gearbox is disassembled on the right side.

i curse myself every time, but then forget and do it again.

i be kevin
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post #7 of 15 (permalink) Old 06-24-2019, 06:56 AM
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Personally, if it was me [that's personally ] I would strip the crank out and clean out the sludge trap and check the big end journals etc....then you're set for the next 50,000. I mean you have gone so far, its not much more to do the lot.
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post #8 of 15 (permalink) Old 06-24-2019, 04:04 PM
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Hi Happyfeet
If you have fallen in love and are looking for a long and fruitful relationship with your T140, then listen carefully to Tridentt150ís good advice.

The T140 has an inbuilt weakness that the T120 never had, the timing side main ball bearing is inadequate for the torque put out by the engine, Triumph tried to mask this by detuning the engine, but the weakness still shows up when you get enthusiastic in your riding, the bearing breaks up filling your crankcase with bits of metal. In 82 Just before they went bust Triumph solved the problem with a special roller bearing.

If it was my bike and I had it stripped down so far, I would take the opportunity to replace that bearing, in the great scheme of things it is not much more work to remove the engine and split the crankcases. Although there are some special pullers needed. As you are not the original owner and do not know the oil change history, once the crankshaft is out cleaning out the sludge trap will serve you well.

Be warned though mission creep can soon set in. Perhaps changing the drive side bearing$$, a crank regrind$$ or polish might seem good$$, and while itís apart get the crank balanced $$restore some performance by changing the cam timing-or new cams$$$ etc.

Good Luck in what you decide
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post #9 of 15 (permalink) Old 06-24-2019, 06:47 PM Thread Starter
Grand Prix 250
Main Motorcycle: 1979 T140E
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Thanks to all who have chimed in and to anyone else, feel free to add. Peg, you are spot on with what CAN happen once a person gets started down the spending rabbit hole, and indeed, I don't know the real history of this bike's care. I bought it with 7300 showing on the speedo from a reputable shop, and the shop owner and I agreed that with a 40 YO bike, ticks on the speedo can't really be relied on. But overall condition and inspection gave me confidence in buying this rig.
I really enjoy hearing from vintage Triumph enthusiasts from around the world. There are good people willing to impart their knowledge and experiences. I'm just an old corn-fed farm boy who has seen internal combustion engines abused to beyond the seeming limit not blow up, and pampered projects that go totally wrong. As far as my oil leak repair project goes, I've decided to stop at pulling the head and leave the cylinder block in place. Everything from head gasket up is getting refreshed seal/gasket wise, and I'm going to leave the valves in the head. I'm rolling the dice that my leak in the front push rod tube base area is just that, a push rod tube leak. The timing cover is going to get refreshed as well with new seals on the crank and cam. I may even let the gear box seal go for another day.
I will keep you all posted.

Thanks again! Best Regards, Robert.
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post #10 of 15 (permalink) Old 06-26-2019, 01:54 AM
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Hi Happyfeet, I did what you are thinking about to very good results. I only had 12k original miles from new though. I've done this to a few motors all turned out good.

After you do tear down you can change your mind at any point.

Mark all tappets, push rods, valves. Do not remove pistons. Pad the rods to prevent nicks, damage. Tape up crank case mouth & pack with lint free rags to prevent dirt from falling in.

But for resealing of oil leaks. You must carefully evaluate motor before tear down, but if it really doesn't use oil now, it won't upon assembly unless you mess up rings.

A few thoughts. Very important do not remove rings!!! If you remove rings they will never seat again on used bore you have now. Do not worry about ring gap if it doesn't use oil. Just blow rings clean with compressed air & some carb cleaner. Only carb cleaner if you don't have compressor. Oil well wrist pin & rings, bore on assembly. I recommend using a ring compressor tool. They make it easy & prevent damaged rings. squirt lots of oil down into big end bearings. Remove carbon from piston tops & above top ring. No need to remove baked on oil from piston sides.

The valves always wear out of round. If you don't remove them, they will be exactly as before. If you remove them, they MUST be lapped using fine compound & suction cup. Don't start with course & go to fine. Just use fine only. The seats will be wide & conical. Don't worry. It won't cause a problem. You can measure stem clearance to guide. They can be very worn & still not use oil & seal fine. However they will tick/rattle like the valve adjustment is too loose. If tip of valve is worn from adjuster screw have them refinished at auto machine shop. Under no circumstances should the face be reground. Do NOT let the machine shop talk you into grinding face. Again only lap the face. Lap the valve until all pits are gone from valve face & seat. Assemble with lots of oil on stem. Make sure perfectly clean. Turn head up & fill the valve recess with solvent or gas. Look inside port with flash light & make sure no liquid is seeping through. NONE! If it seeps you either have dirt left behind or you need to lap more. Don't use drill or lapping machine. Do it by hand with suction cup tool. Keep head held such valve is vertical to prevent side loading while lapping. If valve stem is burred at keeper grooves or stem end, stone or file the burr off so valve doesn't scratch guide on removal.

If you determine guide clearance is too large, then you'll need guides, valves & seats cut with cutter or stone. Every Triumph valve I've tried to regrind face left margin too thin for best operation, so I just get new.

Worn/pitted adjuster screw tips can be refaced to a degree if not too bad. I use a lathe & emery cloth wrapped around a file. But you can put them in electric drill to spin them. Make sure to replicate the radius on end.

You will need torque wrenches & special tools to do this work. The sprocket socket must be deep socket or correct tool. I recommend 1/2 drive or 3/4 drive with 1/2 adapter. I have exact tool # if needed. I always torque the sprocket nut with torque wrench.

Purchase tappet block driver that replicates factory tool. I no longer heat cly or chill tappet block. Place the cyl on 4x6 on concrete floor. Use hammer about the weight of a large claw hammer. Using claw hammer is fine. Look at tool & tappet block. Notice block is not straight but angled slightly. Drive it at the angle that's correct. All O-rings should be viton. Make sure. Except the silicon one at bottom of push rod tube. If... your bike uses the silicon one. Later do not.

Deburr head bore & tappet block bore to prevent tearing O-rings. Even micro tears will leak. Deburr/smooth exterior of tappet block where push rod tube seal will slide over. Very important!

The set screw hole it tappet block is not close enough. Get a 3/4 square bar 12" long from hardware store. Take your square & find the straightest you can. Use it as straight edge. Of course a real straight edge is best, but this will work.

So installing tappet block is not hard. It will want to turn as you drive it. A firm wrist pressure is needed to keep it where you want. Never attempt to turn tappet block while it is stationary. It must be moving while driving to rotate.

Drive down to about 1/4 from home aligning by eye best you can. Then stop & measure with Vernier caliper or depth gauge using your square bar against tappet block ear measuring to spigots of each cyl. Use a marking pen & make an arrow on tappet block which way you want to rotate it. Then drive block down further rotating as you go. If you get home before it's square, no problem. Turn cyl over & drive slightly out while giving rotating pressure. Then back down turning as needed. You can zig zag like this several times only moving 1/16" inch or so. You'll very soon get the hang of it. The next tappet block will be much easier with this practice. Try for at least .003" max difference spigot to spigot.

Good alignment reduces tappet wear in my mine.

Resealing rocker shafts can be hard to get the o-ring in without tearing. I have a good special too to guide in ring. Many don't work well. Buy several spare rings. If you see even a trace of rubber peel off ring it will leak. Deburr & smooth bore in box so it doesn't catch, tear ring. A little smear of silicon on ring is not a bad idea in my mind.

When doing the rear sprocket look close at how deep the seal is. If you put seal too deep it can miss sealing surface on sprocket. Not deep enough & sprocket will rub side of seal. Feel how easy the sprocket turns now. When done it should feel the same or only just a slight more drag. If it feels tight at all something is not right! As was said put sealant on splines even with the o-ring. The o-ring & non oring sprockets are different. The o-ring type is chamfered. Don't use o-ring with non o-ring sprocket.

Pull the seal from inside main shaft with a bent wire hook. They usually come out easy. The rear sprocket seal can be really hard to pull out. I have a slide hammer seal puller, but don't damage the thin trans case in this area while pulling seal. After you remove sprocket the high gear will move in/out a lot. That is normal. The inner face of sprocket is the bearing side race so it should only have a trace of side movement once nut is torqued.

Overall your plan is very sound & straight forward. Doing in frame is how I've done it & works good. Don't scrimp on tools. If you need to force it apart because you don't have proper tool you are at great risk.

Remember you are not improving the motor in any way, just stopping leaks. It will be the way it was, but no more leaks. Suppose you had no leaks? We wouldn't even be discussing this. You'd just be riding it. You could cause damage during repairs by just taking it apart & putting together. So as long as you understand that you are good to go. So give every last part a good visual inspection or measure as you go. Make a parts list as you take motor apart. I'd recommend buying a 1" micrometer & 6" Vernier caliper if you don't have one. They are a must.

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