Triumph Tiger Cub oil burning mystery finally solved?

I took a deep breath and removed the cylinder head again, suspecting a rocker box oil drain hole may have been blocked. Very close, but no cigar - here we see what I think was causing the trouble and how I [hopefully] dealt with it, although the huge gap in the old oil ring threw me off the scent initially. I have had the engine running again, since I made the clip at the end of this video and it does seem far less smoky now and more in line with what might be expected following the fitment of new rings, but the weather turned very wet and nasty, so we remained in the workshop for the rest of the afternoon!

[@sidecarbod1441]

I wonder if you could make some thin-walled hollow dowels that you could put into the holes, if the dowels were tight in the head then the oil would be more likely to go down the centre of the dowel and past the gasket face. You would want to make the dowels the right fit for the existing holes, there is no way you would want to make the holes any bigger...that head gasket looks dodgy enough as it is!

[@williamnethercott4364]

Well spotted! Bike sounds very good. I suppose you already made sure the oil pump was working well (I don't want to sound like I'm trying to teach my granny to suck eggs). It looks to me like the exhaust will clean up with a short run, judging by how it changed during the video. I guess there's some oily residue to burn out of the exhaust.

[@bananabrooks3836]

Good points about the oily residue in the pipe.

[@whalesong999]

Residual oil in the exhaust system could be misleading as to the smoking. Betcha some riding will prove out the situation more.

[@LeytonC]

I would have thought it might have taken a bit of ride to burn off the oily carbon on top of the piston, once there is some load and heat there I bet smoke clear up well. I wondered if it was some old aluminium that had gone porous and was allowing oil to the chamber. Glad it was something you could engineer out, as I was thinking it might be a scrap head.

[@AdrianWhyte]

Hey Paul, have you thought about setting up a Patreon? I would happily give you a couple of dollars a month, I learn more and more watching your channel and I really enjoy the ride ons (and so does my 17 month old son!) I’ve revived about 5 bikes now and recently got my self a 1949 D1 bantam and I’ve decided I want to go right to the crank this time with the rebuild, much inspired by yourself and the classic motorcycle channel. I owe you guys!

[@MURDOCK1500]

I've been having a similar issue with a 1974 Honda CL360. Particularly the RH cylinder smoking and oil snuffing the spark out. I stripped it and found someone had been in there already with new pistons and rings but still on standard bore. I wasn't happy with the rings so I popped some new rings in and honed the bore. And it still blooming smoked??. So I dropped the semi-synthetic oil and refilled it with 15w40 diesel engine mineral oil and fitted a grade hotter long-nosed iridium spark plugs. I then gave the engine some hammer to bed the rings in. Fingers crossed this solved the issue. The rings weren't bedding in because the semi-synthetic oil wouldn't let them and the new plugs are burning the oil off before it fouls the plugs. I hope you've found your problem too. Looking forward to the next video

[@paulhenshaw4514]

Thanks for sharing that!

[@derekgee4223]

Like your in workshop videos Paul

[@johnb5519]

Once again, some good detective work there. I wonder if that excess oil could have stopped the rings from seating properly.

[@johnoregan8245]

HI Paul, I have come across a couple of cub engines that once bored to +40 or more they burn oil in spite of new pistons and rings with correct clearance, It turns out that the cylinder bores become porous once they are bored oversize, I found standard cylinders and once fitted the smoke disappeared !! hope this helps

[@6060don]

Looks like you've done a nice job. Good luck with the Tiger Cub.

[@michaeledwards798]

Tried my bike test in lampeter in the 70,s on tiger cub that was burning oil like no tomorrow, the examiner told me to go round the block and to return where I,d started from, on my return he commented I could hear you going quite nicely changing through the gears up and down but I could not see you I could only hear and smell you ! In this day and age I would of been sent away packing upon arrival if bike was Smokey how things have changed anyway I passed the test and moved up to a triumph 500 twin Daytona t100r what a revelation of extra performance that bike was, thanks for the interesting video,s

[@paullacey2999]

A wee putt down the road is called for... Lovely wee thing!

[@peter7624]

Cigarette? No thanks, I'm smoking a Tiger Cub!

[@bsa_brummie7775]

Definite improvement by a process of elimination. Its good to see someone persevere with each job until it resolves the issues. Can't wait to see it back on the next run. Getting there nice job 👍

[@paulhenshaw4514]

Thanks 👍

[@niallsommerville9941]

Good job and the spare head lives for another day. I don't think there is much chance of us getting bored listening to you fill in all the details that make the job. It's possible you'd be losing a little bit of compression with that leak as well as getting unwanted oil contamination. Thank you.

[@wdhewson]

Wring its neck for 60 minutes on the road to decoke the exhaust system.

[@astrostrotch]

Italian tune up!

[@iivaridark6850]

Yes, those return holes seem pretty close to combustion chamber so the head gasket has a difficult job to do. Rebore didn't make it easier but those (rebores) are obligatory things in time. Let's hope it will be ok! But it runs quite well otherwise!

[@yorkshirebiker1293]

Finger crossed looks like you found the problem 👍👍

[@chevinbarghest8453]

My first bike was a Tiger Cub and I passed my test on one in Harrogate in 1963... I felt like King of the world going uphill at Yeadon steep on my Tiger Cub. Sold it coz the front drive sprocket was round... Sold My Ninja1000 SX (145hp) last year and I am feeling the itch again. Good job it's 62 bloody degrees under freezing in winter here in Wisconsin or I would be out spending... Love the sound of the Cub and I can almost smell the leaky petrol from the cork petrol tap......

[@kevinpollard1550]

Beautiful bike sir

[@paulhenshaw4514]

Thanks ✌️

[@landedzentry]

Thats probably oil in the exhaust pipe? You had a very big suck through of oil . Like a 2 stroke - you get oil burning off in the pipe..as an experiment you could take the pipe off and hang it up over night and see what drains out of it. Getting oil out of a pipe is hard work - fairy liquid, caustic soda - nothing seemed to work on the 2 strokes I had - I would just hang them up every now and then ,..lol

[@Jean-de-lune]

Well spotted! Maybe the residual smoke is from burn-off of oil baked on to the piston head and combustion chamber and could be eliminated after a good de-coke and run.

[@phillipbrown8988]

Quite possible that there was a fair amount of oily deposit in the exhaust pipe which began to burn off once the engine was warm.

[@TriumphBeezaman]

I had a Honda CB125s that had a rebore & pattern piston & rings fitted, everything was in tolerance & fitted correctly so i was surprised to find it burnt a pint of oil going into town & back, i ended up buying original Honda rings & problem solved.

[@paulhenshaw4514]

Exactly the same happened to me with a Honda CB100N - a pattern 'Emgo' piston and rings made it smoke like a destroyer, genuine parts fixed it.

[@bigred8438]

Speaking of British Singles Paul, what do think of the newly released DB34 Gold Star from BSA?

[@paulhenshaw4514]

Not for me, I'm afraid, just as with the new RE and Triumph machines - just another modern machine made to look vaguely like something from long ago and bearing a name from long ago, although at least RE have evolved continuously over time to become something which no longer interests me!

[@brucebrown7691]

Great video as always. Can I ask how did you reface the cylinder head face? I've used a sheet of glass and grinding paste in the past for small two stroke heads but i'm sure there must be a better way.

[@paulhenshaw4514]

Thanks Bruce, I used Emery cloth placed on a flat surface and soaked with WD 40. I started with a fairly coarse grade and finished with 600 grade.

[@brockett]

Well done. A fine example of fault finding by close examination of each part as it's removed.

[@paulhenshaw4514]

Thank you!

[@christineharrison6312]

Yy

[@daveharriman2756]

Looks and sounds promising, and well deduced, nice if you can avoid using the new head too, love to know your tecnique on locating those pushrods back in, I tend to have a nightmare doing them, either goes straight in, or I'm at it for ages, I wish my tube had those guides in, anyway, loving these Cub updates, cheers Dave

[@daveharriman2756]

@@pbysome haha, yes, trouble is the engine is at an angle and gravity doesn't help, the fact that you are trying to locate them blind makes it hard. I first did this to a Cub in '68, didn't seem to have any problem then 😅

[@noeldoran8884]

Well done !!

[@steveburden1801]

Like the trouble shooting vids👍

[@paulhenshaw4514]

Thanks!

[@hermangibbs8163]

Good job!. Thanks.

[@paulhenshaw4514]

Thanks again, Herman!

[@davidvardy2270]

Well done Dr! Sounds spot on!

[@paulhenshaw4514]

Thanks!

[@bananabrooks3836]

Mmmm, still a bit smoky for a four stroke, can you fit a dowel into the oil drain hole to 'sleeve' the joint, or is that not good practice? Also in line fuel filter?

[@paulhenshaw4514]

I ran the engine again a little later and the exhaust seemed a lot cleaner, I think it may be ok this time. I don't think there is enough room for a dowel, unfortunately. Although I found some particles in the float bowl during the breakdown, i don't think they were causing any trouble after all.

[@bananabrooks3836]

@@paulhenshaw4514 Yes, but is that an Amal with the hard to clean pilot circuit? and is the strainer in the banjo bolt doing its job? Good videos, informative and entertaining

[@paulhenshaw4514]

@@bananabrooks3836 Thanks - the carb is actually a Zenith and it has a fairly good strainer at the banjo and another on the fuel tap in the tank. The pilot circuit is excellent on these carbs - note the response when I turn the air screw out one quarter of a turn while the engine is ticking over.

[@leonruthcooke2959]

I put second hand mufflers on my clean burning T150 and it smoked like crazy for 4-5 miles until all the residual oil was burnt out of the mufflers, so the T120 may also take a while.