Hey folks, I’m sure you’re all sick of hearing about this bike with my spate of recent posts, but I’ve been doing some research on what to look out for on these old models and I was wondering how much a problem the original chrome cylinders actually are? It seems that some people are of the opinion that they should be changed immediately for fear of complete engine destruction, but some are even saying that they’ve bought replacement chrome cylinders and are sticking with chrome! I’d like to get a gauge of what people think so I can have an idea of how urgently I should get round to doing it, if I should change the cylinders at all. Thanks!
i’m not sure that one can even buy replacement chrome piston/barrel sets for Tontis?
I’m only familiar with Gutsibits & Stein Dinse: I don’t recall seeing anything but the Nikasil options there, even those are not permanently available.
Anyway, all the advice I have ever seen has been to change chrome barrels at the earliest possible opportunity, if indeed you still have them fitted (which is the first thing to check). To be fair I have also seen people saying that they haven’t bothered and are still running quite happy on them after many thousands of miles. At the end of the day the decision is yours and the risk is yours to assess.
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My loop was running with its original chrome barrels from 1972 until Covid when I was at home with time to spare so I took the heads off to have a look. The left one was perfect but the right had lost a little bit near the top. The problem with the early bikes is lack of a proper filter so bits of chrome can get everywhere. I dropped the big end caps off and there was no sign of any bottom end damage so I concluded the bits had been shot out of the exhaust valve.
The options are to get Gilardoni replacements or send the originals away to be stripped and Nikasil’d. I used Langcourt Engineering for the latter.
As the heads are fairly easy to get off, maybe have a look? Or keep an eagle eye open for flakes in the oil which comes out every time you change it.
Ian
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Thanks to the both of you, I’ll keep a keen eye out for any bits flaking off and hopefully the chrome is still fairing alright as the miles on this bike are still fairly low! Thanks again!
In general the more that a chrome barrel is used, the less likely it is to give trouble. If they fall out of regular use it gives time for the nasty chrome-eating chemicals to get started. If you have the head off and it looks good, gently rub your fingers across the edge of the barrel and in towards the centre. It’s not a foolproof test but oft-times if the chrome is thinking about abandoning bike you can feel the sharp edge before you can see anything.
I think I picked the following up off Pete Roper years ago, but I’m not willing to swear to the source:
- Iron linered barrels are easy to spot because if there’s no rust kicking about, there’s an obvious ring around the top of the barrel where the liner fits
- Chrome barrels have an unmarked spigot from the bottom of the fins to the end of the spigot
- Nikasil/nigusil barrels have one or more very slight steps machined into the spigots.
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If it helps my 1974 850T had chrome bores, these have now been replaced with 950 barrels with cast iron liners (these are possible to rebore or hone) after the lands on one piston (the bit between the rings) broke up and badly scored the original cylinder.
Guzziology rates chrome bores as the chrome is harder and longer wearing, it makes for lighter cylinders that cast iron liners and it expands closer to the rate of the cylinder and piston.
So I guess it is down to your choice and the depth of your pocket. If they are not broken, don’t fix them!
Best wishes Chris
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Ah interesting I didn’t realise that sitting deteriorated the chrome bores worse the running. I supposed I’ll keep a close eye on it and since there seems to be some fairly decent benefits to running chrome bores I’ll keep it around as long as it’s not causing any trouble! Thanks for the advice folks!
I’ve been through the whole chrome flaking thing several times. First was a barn find Eldo that was starting to half moon on the chrome. I sent it to be coated with Nikasil after checking for flakes in the oil in the pan. The second was another Eldo that had new Gilardoni’s and a clean pan, however when I checked the mains during a clutch change I found chrome in the bearings so I rebuilt the bottom entirely. The third is an 850T which had completely trashed the bottom end but had no chrome in the bearings or shells. (It was a late model with the filter in the pan though)
Would I do it all again, no. I would ride it until it fails and then rebuild. The reason is; I suspect that even with failing chrome the bike will just keep on running and when it doesn’t I’ll rebuild it. I have another Eldo that I won’t open until I need to. When I do rebuild I will just get a complete cylinder kit rather than Nikasil the old ones, by the time you have paid for the Nikasil and shipping, waited for it to be done, bought new circlips, gudeon pins, rings etc you could have paid for the whole kit that includes everything.
I guess catching flaking before it trashed the bottom end would save money but what are the chances of catching it in time on a 50 year old bike?