Broken valve

[jetmechmarty]

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My last project was a BSA C11. Spent loads on bike with a top speed of 40mph. Lost lot's of money when I sold it. My wife creates a spreadsheet for every bike I build . She mentions the BSA every time I try to spend on the XS
Just another question.
My cam chain and guides look to be in pretty good condition.
Would it be advisable to leave fifty year old parts in the engine? Are the rubber faces of the guides likely to start falling apart as soon as the engine is started. Bearing in mind they were only thirty years old the last time the engine ran.
I've been reading posts that seem to imply the modern parts aren't always as good as the original ones.
Should I leave well alone, or is this just a false economy.
I'm just looking for opinions
Thanks for all the other help. It's appreciated.


View attachment 243922

What I've noticed here is that the plastic part of the cam chain guide can become disbonded before it wears out. Of the last three engines I opened up, two were disbonded and one was mostly worn out. The worn out one had over 60K miles and no extreme periods of disuse. The other two have unknown history and show very little wear.

 

[SteveP]

I'll probably err on the side of caution, and replace the guides and chain.
I'd rather not have to strip the engine down again any time soon.
Thanks

 

[SteveP]

Hi. Update on the 1974 TX650a.
Thanks again to everyone who helped.
As I mentioned this is a US import to the UK.
The crack in the crankcase, above the sprocket didn't extend into the gearbox. A local fabrication shop welded the crack and I flattened it off then painted the whole case. It seems fine.

A friend of friends who reconditions classic car engines had a check of the head and barrels. Interestingly I was telling him about the XS history and he knew Percy Tate, who sorted the handling out for Yamaha.

It seems as though the 20,000 miles on the Speedo is accurate. The bores just needed cleaning. The guides were within tolerance. The cam and followers were not worn. He managed to recut the damaged valve seat, without recessing the valve too much.

The gear box and crank were fine.

I've rebuilt the engine with new camchain and guides. Cruzinimage pistons. Upgraded starter gear. New tappet adjusters. Stainless steel valves. I'm a little concerned about the valves after reading some posts on this site. Everything has been liberally coated in graphogen assembly paste.

One interesting issue was the breather. It was packed with what appears to be brass swarf. I assume it's supposed to separate oil from air. Later breathers appear to have a perforated screen. A definite improvement because I found some brass in the sump. I've now fitted a reed valve to replace the breather.

I've used Heiden tuning for the majority of the parts. The company is highly recommended. I've fitted their uprated filter and sump strainer.

Thanks again for all the help (so far)

 

[Vincenthdfan]

Hi. Update on the 1974 TX650a.
Thanks again to everyone who helped.
As I mentioned this is a US import to the UK.
The crack in the crankcase, above the sprocket didn't extend into the gearbox. A local fabrication shop welded the crack and I flattened it off then painted the whole case. It seems fine.

A friend of friends who reconditions classic car engines had a check of the head and barrels. Interestingly I was telling him about the XS history and he knew Percy Tate, who sorted the handling out for Yamaha.

It seems as though the 20,000 miles on the Speedo is accurate. The bores just needed cleaning. The guides were within tolerance. The cam and followers were not worn. He managed to recut the damaged valve seat, without recessing the valve too much.

The gear box and crank were fine.

I've rebuilt the engine with new camchain and guides. Cruzinimage pistons. Upgraded starter gear. New tappet adjusters. Stainless steel valves. I'm a little concerned about the valves after reading some posts on this site. Everything has been liberally coated in graphogen assembly paste.

One interesting issue was the breather. It was packed with what appears to be brass swarf. I assume it's supposed to separate oil from air. Later breathers appear to have a perforated screen. A definite improvement because I found some brass in the sump. I've now fitted a reed valve to replace the breather.

I've used Heiden tuning for the majority of the parts. The company is highly recommended. I've fitted their uprated filter and sump strainer.

Thanks again for all the help (so far)

Wow, you've been busy!

That chain damaged case repair turned out great by the way.

 

[SteveP]

Thanks for that. I am pleased with how it's progressing. It's a very nice engine to work on. Spares ain't cheap though.

 

[Adamc]

Thanks for that. I am pleased with how it's progressing. It's a very nice engine to work on. Spares ain't cheap though.

Shame we didn't get a full post on the engine rebuild.
Nice work however and the finish on the motor looks great.

 

[Its been a long time]

Thanks for that. I am pleased with how it's progressing. It's a very nice engine to work on. Spares ain't cheap though.

You might already know these guys but they can repair just about most things on this type of engine. Seager Engineering, worth calling them if you have engine bits that can be saved.

http://www.seager-engineering.com/

 

[SteveP]

I've only just realised that I don't take photos as I do rebuilds. Loads of photos as I strip things down.

 

[SteveP]

I was going to start a new thread about carburettors. But there's so much information already on this site. I'm nowhere near rebuilding my carbs yet.
I'm really just looking for some opinions.

I'm starting to think about rewiring the TX650. The switches had wiring running in the handlebars, which are bent. New handlebars will have the wiring outside.

I've managed to modify the left hand switch. The right hand isn't easy to modify so I need a new switch.

The 1974 switch has a twin cable throttle, later switches have just one cable.

I've acquired another set of carburettors from a 1976 XS. The new carbs are linked for one cable and the original ones are separate, for two cables.

I'm just wondering if there is a massive advantage to fitting the later linked carbs, or are the original ones fine.

 

[jetmechmarty]

I was going to start a new thread about carburettors. But there's so much information already on this site. I'm nowhere near rebuilding my carbs yet.
I'm really just looking for some opinions.

I'm starting to think about rewiring the TX650. The switches had wiring running in the handlebars, which are bent. New handlebars will have the wiring outside.

I've managed to modify the left hand switch. The right hand isn't easy to modify so I need a new switch.

The 1974 switch has a twin cable throttle, later switches have just one cable.

I've acquired another set of carburettors from a 1976 XS. The new carbs are linked for one cable and the original ones are separate, for two cables.

I'm just wondering if there is a massive advantage to fitting the later linked carbs, or are the original ones fine.

The 1975 bikes were popular. Nobody was complaining about throttle cables. With time comes innovation and improvement. So now, you have to decide if you want to ride the original bike or an improved version. OR, just stuff it and go buy a new Royal Enfield.

 

[SteveP]

I'm thinking I'll stick with the original carbs. I got the new ones because they had supposedly been rebuilt. I'm hoping some parts will be interchangeable, if necessary.
Forgot to post picks.

 

[SteveP]

I just got rid of a modern Bonneville. Nothing to tinker with

 

[jetmechmarty]

I just got rid of a modern Bonneville. Nothing to tinker with

Yeah. Keeping them going keeps one going!

 

[gggGary]

I'm thinking I'll stick with the original carbs. I got the new ones because they had supposedly been rebuilt. I'm hoping some parts will be interchangeable, if necessary.
Forgot to post picks.

Tread REAL carefully on parts swapping....
Those BS38's all LOOK similar but near zero parts interchange tween early and late units.

78-79 type are usually called the best BS38's
As 5twins is fond of saying; the 76-77 carbs fitted the smallest main jet ever used on the XS650, the jet needle, needle jet and pilots had to compensate.
78-79 type are usually called the best BS38's
But I've had 70 carbs that ran "fine"

 

[SteveP]

I've started wading through the various carb threads. A bit of a can of worms. I'm not at all knowledgeable regarding CV carbs. A bit of a steep learning curve. It'll be a while before I get round to the carbs.

My idea is to rebuild the US carbs to the richer European spec. There's a document from the Dutch owners, that's been posted on this site. If that's possible?

I've also acquired a Marshall exhaust system so that may add another complication to the jetting.

 

[jay760]

Your small ends looked shot, though they normally are with just a thin smear of copper coating, you can see the copper on the front and back but worn out on both bottoms, can't see the top,
may be an optical illusion but the oil feed for the head the thread in the crankcase looks non existent and the hole looks oval

 

[SteveP]

I did check the small ends carefully and they seemed fine. A friend who's built a couple of these engines had a look as well any thought that they were okay. I believe it's only done around 20 000 miles.
The oil feed thread was fine. It's probably my rubbish photography

 

[Melnic]

I just got rid of a modern Bonneville. Nothing to tinker with

Tangent to this thread:
My solution was to keep my Bonneville as I can easily fit 4 (maybe 5) bikes in my garage
Its a great bike (mine is a 2022) and I got a wacky great deal on it.
I agree, nothing to tinker with, after adding bags and crash bar, everything else I left stock.
Once I get my XS650 running well, it will definitely take away from my short local 1hr recreational trips after work I take on the Bonneville.

How do people in the UK feel about the Bonneville made out of country? Is there still any loyalty to them within UK?
I will say this, it was the best Modern classic I test rode and why I got it. Engineering is very good IMO

 

[SteveP]

Mine was a 2011. Air cooled fuel injected. It was a bit snatchy at low revs. I did a stage 1.5 tune. Remapping, modified airbox, removed emissions control and more open silencer. Really nice sorted bike. Reminded me more of a Norton commando than an old bonnie.
Unfortunately I moved house and needed some cash and room.
I'm not sure anyone really notices that the later ones are made in Thailand.

 

[Melnic]

I knew they switched to Thailand and I was surprised when I mentioned that to the dealer and he said the country of Origin for m 2022 T100 was India. I knew Triumph was moving some stuff to India at the time but I still can not see any info that the T100 was made in India. I do search around periodically for a good condition fair priced Bonneville made in UK. I will have to give up an old Yamaha (not the XS) to fit it in my stable though.