This was a thread on my struggles with my 69/74 bitsa. http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=689483&page=13 Because of the broken photo links thanks to photo bucket I have decided to start a new thread on the engine and gearbox rebuild along with new fotki photo links. I may eventually go back and fix the links in the older thread but right now I have better ways to spend my time. Where that thread left off I had made the bike rideable and it was actually running pretty good, good enough for me to take it on some longer rides and find out the oil pressure was marginal at best at sub 40psi at 4000 rpm. The clutch was also slipping badly, so the primary had to come apart. Once I got it apart, I decided to go ahead and strip the engine and replace the bearings. Here's some pics from the strip down. Here she is before the strip down Hosted on Fotki Badly glazed clutch, will replace with new. Hosted on Fotki Drive chain sprocket was a fight getting off. Heat and an impact gun finally got it. Had to special order the socket Hosted on Fotki Head off. I have recently replaced the valves. Hosted on Fotki Top cylinders, compression was 140,135,130 Hosted on Fotki cylinders off, pistons had been knurled at some point, standard bore will go +20 and new pistons and rings Hosted on Fotki Cylinders are glazed and show some light scoring. Hosted on Fotki gear box apart Hosted on Fotki More to follow.
If this engine could talk it probably could tell some tales. Definitely some hard object in the timing cylinder. Piston is getting replaced and I removed any sharp edges from the divot in the head to prevent hot spots. Bottom end is from a 69 while rest of engine appears to be 74 same as the frame. More tear down pics. Crank has been reground at least once. When I miked the journals I found the rods were -.010 but mains were actually -0.20, no indication stamped anywhere. Hosted on Fotki Main journal showing scoring. I'm thinking maybe on the second regrind the cleanout plugs weren't removed and debris damaged the journals Hosted on Fotki Main bearings. Also the caps were switched side to side. Guess the po didn't know what the t & d stood for. Being a 69 the caps had the rocker feeds but they were blanked off. Hosted on Fotki Typical rod journal Hosted on Fotki Rod bearings Hosted on Fotki Exhaust cam has a divot in it, its getting replaced. Got a good deal on the pair, so a new intake too. Hosted on Fotki Lifters are badly scuffed so new stellite tipped ones Hosted on Fotki I seriously debated whether to strip this engine or not. Based on what I've seen I'm glad I did. Crank and cylinders went to Big D in Dallas for a regrind and +20 over bore.
I do not think the scoring on the journals is from a previous regrind. There is only the cross drilling for the oilways and plugs, not a clean-out per say. Dirt trapped beyond the hole to the bearing will stay there from centripetal force. Anything up to the bearing hole or dirt in the oil will get to the journal. As an alternative to grinding the crank further you can have the journals hard face built up and reground for nearly the same cost. They would be less sensitive to scoring.
Thanks for the suggestion DM. Crank has already been reground. I still have one more grind on the mains and two on the big ends. Hope I never need to see the crank again. Considering my age and amount of miles each bike gets, if its done right I shouldn't. Timing gears installed today. Hosted on Fotki Strange grooves on one of the drive side tappet blocks. Has two matching grooves on the other side but not as deep. Almost like the tappet was forced from side to side. Tappet fits in there nice and smooth now and doesn't rock side to side. Wondering if it would be okay or need to replace. Not sure how to replace it. All of the tappet tools I see for sale have 2 pins. No instructions in manual. Hosted on Fotki
My guess is the face of the tappet was not square to the shaft. Your tappet faces were fairly scuffed. As the tappet was lifted it would twist twist one way then twist the other on the falling side. There is a plug in the face of the cylinder base (70-9465) that orients the tappet block. The cylinder flange must be supported when driving the tappet block in or out. There is an o-ring seal (70-6560) around the tappet block that should be replaced also. You should blue the tappet faces and check the cam does not run off the face. Very quick cam wear will follow.
When I tore my T150 down one cam follower was crossways from the factory and the result was these same grooves. Install a new follower correctly and it should be OK. The bike only ran 1662 miles to make those grooves and destroy the cam lobe.
Last edited by GaleGorman; 08/13/173:42 pm.
Gale Gorman Houston 1974 Triumph Trident 1983 BMW R100S
Thanks for the replies. . It looks like replacing the guide blocks on these is close to impossible. There is a dowel that holds them in place and the dowel is driven in flush with surface of the casting and then staked with a punch. I don't see anyway possible to remove the dowel as it can't be driven out and there is nothing to grab to pull it out. One other question I have is on the tappet there is a flat with a hole in it on the stem. How should these be oriented. My cases are from a 69 but the rocker feeds have been capped at the main bearing caps. Hosted on Fotki
One other question I have is on the tappet there is a flat with a hole in it on the stem. How should these be oriented. My cases are from a 69 but the rocker feeds have been capped at the main bearing caps.
The dowel pins are removed by drilling a hole and tapping them then use a slide hammer. You should be able to get a #10-24 in there if you can find centre. Remember the tappets are not square to the block so press them out and in square to the hole.
I think Gale nailed it, the tappet had been incorrectly installed turned 90 degrees. When I turn it that way it fit the grooves perfectly. Hosted on Fotki The cam lobe also had a v-shaped wear pattern. It was getting replaced anyway. Hosted on Fotki Here are the tappets installed after I had the bores reamed to .5 to 1.5 thou clearance. If you read my other thread you saw 3 of the tappets had oversized stems. Hosted on Fotki My lovely better half assisting me dropping the cylinders on. Hosted on Fotki Cylinders on, I used the middle piston in the cylinder method and then added the rod cap through the sump opening. Took 2 tries but last one went well. Everything rotates super smooth. Hosted on Fotki All buttoned up and ready to drop back into the frame. Need my ex linebacker son in law to come up and give me a hand.
My son in law came up the other day and picked up the engine and slid it into the frame like it was a loaf of bread. Here she is already to start bolting parts back on. Not sure whether to do the head or gearbox next. Should be plenty of time to work on it. Looks like we won't be riding any motorcycles in the Houston area for a while. Hosted on Fotki
Back on track after a bit of a set back. After I got the top end assembled I found a plastic bag with two dowels. Carefully going through the parts book I determined they were supposed to go between the crankcases and cylinder block. So long story short, the top end came back apart, dowels and new gaskets installed and everything buttoned back up again. Next install was a new NOS oil pump. Hosted on Fotki Testing the pump and priming the engine. 100 psi oil pressure and return to oil tank. Hosted on Fotki With good test on oil pressure, I assembled the gearbox. Hosted on Fotki Hooked 20 tooth gearbox sprocket. Needs replaced Hosted on Fotki Next task the clutch and primary.