1978 T140E top end woes - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 10 (permalink) Old 11-08-2016, 09:52 AM Thread Starter
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1978 T140E top end woes

I have run into a few problems with the top end work I have been getting into over the past few weeks.

Recap: 1978 T140E purchased over the summer. Was getting poor compression out of one cylinder and the push rod tubes were leaking oil so I took the top end off to investigate the compression and replace the PRT orings/crush seals. I discovered that at some point a previous owner put a mismatched set of pistons into the bike (photo attached).

The cylinders were measured and determined to be standard size and still within spec so ordered a new set of pistons and rings and began to reassemble to barrel. When putting one of the inner head bolts back into the cylinder with a little WD40 I noticed liquid bubbling out of a micro sized hole on the cylinder wall. Meaning that the cylinder wall has a hole/hair line crack (casting porosity) that is connected to the threaded hole of the inner head to barrel bolts about 3/4" from the top of the barrel. I was just finger tightening at this point so I do not think I created the hole, my assumption is that it has been there for quite sometime.

Is this a common problem? What are my options? 1) run as is, I assume this is a bad idea although I also assume it has been running like this for some time. 2) have the barrel sleeved. (anyone know of approximate cost/a good shop)? 3) buy a new barrel (any insight into a high quality one is appreciated).

While I have the head off I tested the valve seating by turning the head upside down and pooling kerosene into the cupped area where the valve contacts the valve seat, liquid is leaking down. I will remove the valve and inspect/lap in the valves.

Is there a way I can test the valve guide ID without a split ball gauge?

IS there a way to test the fit/sealing of the valve guide into the head body?

Any and all help is appreciated.
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post #2 of 10 (permalink) Old 11-08-2016, 12:43 PM
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You need a replacement cylinder barrel and pistons. A used barrel can be better than a new one.


If the valve doesn't wobble in the guide, that's good enough.

Can you pool kerosene around the top of the guide, to see if it leaks down between guide and head casting? If it leaks and the guide is not loose, seal it with silcone sealant under the spring seat.
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post #3 of 10 (permalink) Old 11-08-2016, 01:10 PM
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If you mean there is a pore between the head bolt threaded hole and the OUTSIDE of the cylinder (between fins), that's not a problem at all, and my guess is it's at the bottom of the hole. Castings are imperfect, but not mechanically un-sound.

If you have any perceptible valve wiggle in the guide, take it to a machine shop and have them check the actual wear and ensure it is within tolerance. You'll have a very noisy valvetrain otherwise.

Definitely buy a hand valve grinding tool, and 1 tube of coarse, 1 tube of fine grinding paste and try hand-lapping the valves to the seats. Also, whip out a magnifying glass and check the valve lips and seat faces for pitting. After lapping, try the kerosene test. Should hold for a good 1/2 hour.

It's not rocket science and often is all you need IF your valve stems and guides are not worn.

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post #4 of 10 (permalink) Old 11-08-2016, 02:06 PM Thread Starter
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Tritn Thrashr - I was wondering if there was enough room to collect liquid at the top of the guide to do just that. I ordered a valve spring compressor this morning so hopefully by this weekend it is here and I can pop them off and have a look and see if anything is leaking down. I like that if the guide is stable and leaking I can just use some high temp silicone. I hope at worst this is the case and that the valve has no noticeable wiggle in the guide, I have already bitten off more than i would like to chew on this project taken into account the cylinder/piston issue.

GrandPaulZ - I mean there is a micro sized hole in the inside of the cylinder wall, I have attached a photo showing the best I can the area. The hole is not visible to the naked eye unless you are forcing fluid through it. I would assume if I used as is I run a great risk of the hole inlarging and causing more issues or gasses escaping this hole and going up/out the bolt hole.

I picked up a hand lapping tool with the suction cups over my lunch and some Permatex grinding compound as it was all my local auto shop had. No grit is listed on the packaging but doing a little research on line shows that it starts as 120 as you lap the valve it goes to 150, 180, 220 as the aggregate breaks down.

here is the product - https://www.amazon.com/Permatex-8003.../dp/B000HBM80M
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post #5 of 10 (permalink) Old 11-08-2016, 02:21 PM
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That needs new liners, or a replacement cylinder.

If you go with new liners, you NEED to have a shop that has done them SUCCESSFULLY before.

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post #6 of 10 (permalink) Old 11-08-2016, 02:39 PM Thread Starter
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That is what I was afraid of. As far as I know there are no shops around here that work on British or vintage bikes outside of HDs. I have never been able to convince any of the local shops to even consider looking at my Enfield or this Triumph. I am in the Williamsport, Pennsylvania area about 1.5 hours north of Harrisburg and an hour NW of State College. If anyone knows of proven machine shops to work on bikes in this area please pass on this info.


I would assume a re sleeve is easily $200 + with a reputable machine shop and with me not having one around here I would have shipping both ways involved. I can pick up a new head from British Bike Bits/Burton Bike Bits for $350 delivered from the UK. I am going to sit on it another day or two but I think a new cylinder is in order. This may be a foolish question but I should not have to do anything to the new cylinder outside of clean it correct? The Cylinder bores should be to finished standard dimension already honed?
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post #7 of 10 (permalink) Old 11-08-2016, 04:19 PM
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Ask Burton about the cylinders they sell.

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post #8 of 10 (permalink) Old 11-08-2016, 05:56 PM
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The two inner 5/16" studs are/were installed upside down. Running the end of the thread up against the cylinder head surface leads to distorted bores, or worse. For that matter so where the 4 outer 3/8" studs, but they did that at the factory and at this point another story.

All Triumph hardware (torque figures) assume you assemble dry.

Depending upon your budget I would get a new, or used cylinder. You should be able to get a 71-4005 cylinder new stateside for a little bit over $400-450. To be honest I would like the cylinder semi-finished so I could set the clearance and surface finish myself.

There are two cylinders available: AERCO made in England and LF Harris made in Taiwan. Both can have personalities.

On the 750 there is very little material in the casting to sleeve it. The area around the 5/16" inner studs is very thin to start with and the cuts to allow a wrench to go over the cylinder base nuts leave very little of the casting available for sleeving. It would be a crap shoot at best to try to sleeve it. Considering decent sleeves are running over $100 each, and add labor, the finished job would only cost a little less than a new one. Then the cylinder would be so thin that it might fail in short order.

The closest shop that I would recommend is in Honey Brook PA - Long's Custom Service 610-286-5870. But like most places in PA you can't get there from where you live. That is in any kind of straight line. It is a specialty machine shop does Harley to Vincent.
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post #9 of 10 (permalink) Old 11-09-2016, 09:52 AM Thread Starter
Grand Prix 250
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Quote:
The two inner 5/16" studs are/were installed upside down. Running the end of the thread up against the cylinder head surface leads to distorted bores, or worse. For that matter so where the 4 outer 3/8" studs, but they did that at the factory and at this point another story.
Johntion - Thank you. I have attached two photos, one of the 5/16 and one of the 3/8. From my parts manual it looks like the 5/16" bolt should have the end with the non threaded machined cap facing down into the barrel, is that correct?

on the 3/8" bolt it is not clear from the parts book if the end with the non threaded machined cap should face down into the barrel or up to the head.
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post #10 of 10 (permalink) Old 11-09-2016, 01:02 PM
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Putting a liner in a bore that is cracked sounds daft to me.
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