Putting together a 1969 T100 engine. Crankcases together, new barrel fitted with high domed new pistons/rings etc. Put cylinder head on with head gasket (thick type) as a dry run, rotated engine and discovered pistons are fouling the head by a miniscule amount enough to excert pressure past an obstruction to the rotating action of the engine. A very faint abrasion can be seen on the exhaust valve side of the piston.
What is going on? Been told my cylinder head is the wrong version for HC pistons. Could it be that the head is from a 5TA or T100A of early 1960's vintage. J.R. Nelsons book 'Triumph Tiger 100 and Daytona' mentions that alloy cylinder head fitted to the 1960 T100A was carried over from the earlier 5TA but was fitted with 9:1 pistons with no mods to the head. I'm confused. What kind of head do I have ? For what it is worth, the cast number on the head is E3991
earlier and 67 on heads differ in their combustion chamber. Also, an early 9 to 1 piston and a 67 on 9 to 1 piston are quite different in shape. This may not solve your problem but a picture of your head's combustion chambers and your pistons will go a long way to solving the problem. It's also normal to use the 24 thou gasket rather than the 48 thou one. One problem would be possible oil leaks at the pushrod tubes with the thick one. Post a couple of photos and you will get lots of help. Cheers, Wilf.
Jim. just had a look at a couple of my heads. The pre Daytona head is E3991. My Daytona head is E 6851 so if you have 67 on Daytona pistons with that head, there is no way that can work. The later piston's crown starts right at the edge and the crown on the earlier piston starts about 1/4 inch in, so their not compatible. You could go to early pistons ( 7:1 or 9:1 ) or find a later head, which would be correct. Anyhow, take off the head and have a look and you will see the difference. Post photos if you can. Cheers, Wilf.
earlier and 67 on heads differ in their combustion chamber.
Another difference is that '69-on Triumph changed the inlet mounting studs/Allen screws, from 1/4" to 5/16" dia. and BSF to UNC threads (in the head - studs had Cycle or UNF threads respectively on the 'nut' ends).
Sounds like a good excuse to ditch the hi-comp pistons for some stockers. The engine will run better, be less vibratory, easier to start, more reliable and all-around much happier. Hi-comp pistons are great for racing and for those who don't ride their bikes very much. Just my 2c... If you must have hi-comps, using a thicker head gasket is the cheap way around the problem. Proper solutions will take time and money. Better check that the valves have proper clearance too. "Not hitting the piston," is not how you check these things. If you feel that you're out of your depth with all this, stick with the stock set-up. (There I go again!) And, yes, I ride a stock Daytona and it's one of my favorite all-time bikes.
When people who should have known better cautioned me about the dangers of motorcycle racing, I always told them that a fear of death is nothing more than a fear of life in disguise.
Re: T100 cylinder head dilema
#229362 12/23/0810:42 am12/23/0810:42 am
Sounds like a good excuse to ditch the hi-comp pistons Hi-comp pistons are great for racing and for those who don't ride their bikes very much. I ride a stock Daytona and it's one of my favorite all-time bikes.
Aiui, this isn't about hi-comp pistons; it's about the difference between squish-band (early) and non-squish-band (late) bits. Your stock Daytona would have 9:1 compression and I suspect it wouldn't be quite so favourite if it had something like the stock lower (7.5:1?) compression.
Many thanks for all the info received relating to cylinder head/piston problem I have. I am away from my garage until Sunday 28th December so cannot takeany fresh photos until then, but here are a couple of pictures I have on my camera, taken a few days ago. The High Dome pistons can clearly be seen. I will post some pictures of the head on Sunday, but I am leaning toward getting hold of the low dome pistons as soon as possible. Regards jimsigs
9:1 IS stock in that engine. what Stuart and Gordo and I have said is that your problem seems to be one of a mismatch between the correct pistons for your engine and the incorrect head which seems apparent from the number E 3991. It probably wouldn't be hard to find a trade for the correct head as your head is not as easy to find as a Daytona head. It took us forever to find a E3991 while half a dozen later heads showed up over the last few years. I've been running 9:1 pistons in my Daytona forever and just now putting in new ones which are 9:1 as well. It just wouldn't be a Daytona with anything else. Get the right head and enjoy the sweetness of that engine. Cheers, Wilf.
looks like my last post vanished into the ether. Wow! Maybe your best bet IS to get some of the older style of pistons, perhaps without rings so you can use the rings from your Daytona pistons. A couple of years ago we got a pair of 5TA pistons from L F Harris in the UK (+40), a pair of "MC" 9:1 pre Daytona (+80) on eBay, and just recently, I ran across a NOS set of Hepolites at +40 and 9:1. If you would like to go the way of changing to the older piston type, our local supplier does have a lot of NOS stuff and if you can't find what you want in England, he might have something. I guess we'll hear from you on the 28th with some photos. Merry Christmas. Cheers, Wilf.
There are alternative foreign made "flat tops" available, but a couple of people I spoke to didn't like them. It seems that the problem is they're heavier than the Heps that they replace. If your engine has been balanced then this could be a stroke of luck, the weight being closer to the weight of your originals than Heps would be (had a long talk with a balancer local to Swindon about this when I was trying to find some Heps).
Wilf, What sort of price do the late T100 heads go for where you are? Merry Xmas
I have another alternative up my sleeve. I have a built up 1966 T100SS engine in a 1964 T90 frame. (picture below) So what I might do for now is to use THAT head which is what I'm after anyway, because that bike is also fitted with a new barrel & high dome pistons AND the engine has been run up anyway. Then when I get around to swopping engines, I will worry about finding a head for the T100SS engine, which I will in the fullness of time dispose of. That will leave the 1969 T100S engine in the T90 frame.
Hey Paul. Three or four years ago, I sold a 69 ish head which had been beadblasted, no broken fins, not recessed seats and in beautiful condition for 200 cdn. Someone really needed that head and that was what I was offered. A few months ago, I bought a couple of boxes of stuff including a good useable head with one corner of one fin missing, a barrel at +20, a set of 69 cases ( repaired ) a good crankshaft and a bunch of other bits like gears, pushrods etc., for less than 400 cdn, so I guess it depends on where you be and who wants what. In this area, it seems that the 650s get most of the attention and the 500s not so much. I have bought heads needing repair such as exhaust port rethreading or just for a fin donor for less than 50 cdn. What could be found today is anybody's guess but the two boxes of stuff I recently got was advertised for two or three weeks with no takers until I showed up. The only reason I find this stuff is by picking up the local area Buy Sell Trade every week and letting the nearby Britbike dealer know that he should let us know first about any stuff for the bikes we have, and it seems he's always finding something we can't live without as he actively seeks out loads of stuff from old dealers and basements.
Hope that gives you some idea....and, of course, apart from that head that I sold for 200, it's not often that you will find a head that doesn't need some work. Cheers, Wilf.
Hi Wilf, thanks for the info. We've got relatives in BC & a couple of friends emigrated to Nova Scotia last month, so I'll ask them to keep an eye open for me. When the classic bike craze started here, the attention was on the 650s & the 500s were pretty much ignored, just as you say is happening where you are. Once T120s started reaching silly prices, people started looking at T100s as cheaper alternatives. Then, it seems, they realised what sweet little bikes they are, once years of wear & bodges are fixed, & there's now a number of people actively searching out nice examples, particularly the late models, hence the high prices & the sudden scarcity of parts. Grab as many parts as you can while they're still cheap!!! Happy New Year cheers
Hi Jimsigs. As suspected, you appear to have the early head complete with 4014 manifold. If you find a later head, you will also need the later single carb manifold as they are not interchangeable. If your 69 engine is a C or an S then a Concentric 626 would be the carb to use and if it is an R or a T then two 626 s would be the choice although many use a single 626, 928 or, as I do a single 930 on my Daytona. The main differences are cams, followers and subsequently, which timing marks you use on the camwheels. I use the Daytona cams, camwheel positions and Daytona followers with the 930 carb. A later head will have, at least, larger inlet valves.....anyway, that stuff is all in your Daytona book by Nelson. It's also very useful to have the detailed year by year specifications booklet that goes along with the T100/Daytona book that you have. Nice looking T100SS/T90. Enjoy the process. Cheers, Wilf.
Thanks for the input. I'm OK with info on carbs etc as the T100ss has a Concentric 626. however, my 1969 T100 is an 'S' and has matching crankcases and crankshaft. I have also fitted new crankshaft bearings.
I rescued some camwheels from a 1960 T100A and have set them upon the dot. They only have one keyway anyway and although I pressed into use the T100A inlet camshaft, I had to obtain a new exhaust camshaft as the T100A one was no good for the points in the timing cover. Incidentally, I have all the kit for the 1969 timing cover complete with oil pressure valve on the actual timing cover itself.
Thanks again Wilf.
PS Just on another subject, i came across some of your Countrymen when i was serving in the Commonwealth Infantry division in Korea - 1954. I remember the whiff of the Sweet Caporal cigarettes. I also remember visiting the Sgt's mess of the Princess Patricia's Canadian Light infantry. Useless info but good memories.
hey guys , reviving this thread instead of starting a new one because most of the pertinent info is already here .
'67 t100c h56429 , , tore down my top end this past weekend to find it has the earlier head/manifold . actually kinda psyched in a way having a perfect early head and finding original bore with just very minor scoring , so a +.10 or .20 will be good to go .
i've found plenty of sources for hepolite and import pistons for the early head and aren't they both 9:1 ? what makes the later one better?
Woody! yes, they can both be 9:1 but they are different and not interchangeable. Combustion chamber shape, piston shape etc. The early pistons go with the early heads and the late pistons go with the late heads although an early piston can go with a late head to reduce compression ratio but a late piston cannot go with an early head as has been explained on the first two pages. As long as you have early/early or late/late then carry on. Cheers, Wilf.
"my question is , is there any advantage , performance wise , to upgrading to the later setup ? "
On paper you could say Yes. As a practical matter, No.
It takes a lot of time and money to make one better than the other. In my opinion, the choice in your case would be between which head requires the least amount of work.
The later set-up does allow you to fit dual carburetors. The early set-up has a useful squish band (though you need to know how to set it up. The later set-up has better valve angle. The later setup has bigger valves. The early setup has the potential for more low end torque. I like the early head for performance applications... Phantom 309 likes the late head. The early head is a LOT of work to get performance out of. The later head is a LOT easier to get performance out of, but neither would end up stock and you would have to spend a lot of money...
Six of one, half dozen of the other... Pick the best head, do a good valve job, and enjoy! John