Alignment concerns (crank > cylinder)

[Radlan2]

Hi Folks
     We must all like to keep perfecting/improving our machines as is evident from the postings. I have read about crankcase to barrel faces being out of true and wonder if anyone has experience of this, I know SRM offer a service to reface the crankcase.
     I have an issue which is bugging me, I fitted a pair of the new pattern Hepolite pistons and 1200 miles later decided to strip the engine to change the 356 cam to a 357. when I went to remove the gudgeon pins I found both only wanted to slide towards the drive side probably because a burr had been raised. I changed the cam and all is now back together but it is making me wonder if I have a problem.
      I know the barrel faces are parallel, I know the big end small end bores are true, I think I can take for granted that the gudgeon pin is true to the piston. What I dont know is true is if the cylinder bores are true vertical to the crankshaft.
      I would like to measure the piston/con-rod relationship in the bore of the assembled engine using a scrap piston with the top cut off so I can see and check the rod is central. Good idea?   Anyone got a scrap +o.060" piston they would like to donate?
                    Interested in any thoughts.
                            Chris Protheroe

[chaterlea25]

Hi Chris,
If the piston are running cockeyed in the bore, there will be uneven rub marks on the pistons , can you post some photos?
The other way to check the bores is to set the cylinder up level on a milling machine table and run a dti down the bores from the spindle

John

[BigJim]

Not all of us Mr Radlan2.
 
Just everyone else, I deffo ride rather than fix. Doesn't mean i don't hand over wedges of cash to " engineers" every now and again. I do give it stick tho and get a lot of pleasure out of it. In truth i reckon lots here get as much pleasure out of the building and fixing.

[Radlan2]

Hi John
       Thanks for the reply
              I didnt take any pics and the engine is back together now, I would have noticed any polished high spots on the piston, there was nothing except the odd thing with the small ends. Another serious thing though is that the bore became very worn and polished, not front to back as normal but all around and I think this is due to the (steel?) rings supplied when I bought the pistons. They are not as supplied by Hepolite but some other make which seem to be too hard on our cast iron bores.
               Because of this I am replacing the barrel/pistons with a second set which have been freshly rebored (by SRM after your recommend in a previous post). The pistons are Genuine BSA 67-1604, hence pretty irreplaceable so I am trying to forsee any possible further problems.
        Best Regs
               Chris

[Radlan2]

Hi Big Jim
    First of all I have to say"I've got it bad" and I do get as much pleasure out of building them as riding them and by riding I mean absolutely thrashing them and to do that everyting must be absolutely spot bollock on. The only safe way to ride like that these days is on a track which I do in the UK and the continent (but not for a while...). The satisfaction and excitement of riding something you have built yorself, on the limit is so rewarding. To be clear I am not a racer, just a track day hero, I dont go barging people out of the way to get past but do ride as fast as I can.
       I like my bikes to be road legal, for me the best way to get them running at their best is on the road. I used to work in the newspaper industry so saw the headlines of people getting smashed up as soon as there are a few sunny days,I  try not to take any chances on the road, we all know the risks.
         Hey lets be careful out there.
                 Best Regs
                          Chris
                     Chris

[Triton Thrasher]

All I can offer is that a circlip raising a slight burr in the alloy of the piston is common and a bike can do a lot of miles like that.

[Radlan2]

Hi Thrasher
      You could well be right there, I didn't take enough notice of it at the time and am now overthinking things. By the way we have met, I am the guy with the T160 who wouldn't give you my spare clutch cable for your Trident at the ferry port, was it Portsmouth? I read later that you completed your trip to, was it the simmer dim rally? something like that, top of Norway without a clutch. I salute you..
       I was on my way to the TR3OC rally in Munich, did my best single days riding ever of over 600miles in a day, and the clutch cable didn't break.
             Best Regs
                     Chris

[Triton Thrasher]

Hi Thrasher
      You could well be right there, I didn't take enough notice of it at the time and am now overthinking things. By the way we have met, I am the guy with the T160 who wouldn't give you my spare clutch cable for your Trident at the ferry port, was it Portsmouth? I read later that you completed your trip to, was it the simmer dim rally? something like that, top of Norway without a clutch. I salute you..
       I was on my way to the TR3OC rally in Munich, did my best single days riding ever of over 600miles in a day, and the clutch cable didn't break.
             Best Regs
                     Chris

No I don’t think that could have been me.

[Radlan2]

Ooh, always thought it was you, not the sort of thing you 'd forget, well hats off to whoever it was.
          Best Regs
                Chris