Mike Yeadon's GT550B that is. After open heart surgery over the last 3 days, it now has iron bore schneurle port barrels and +1mm pistons fitted and ran lovely yesterday on a quick run around the local village.
The original barrels were sloughed in the inlet/schneurle port areas but no sensible reason for that. Plenty of oil and everything seemed ok, but even Sherlock would have been stumped!
Anyway thanks for the hospitality Mike, except for Monday night of course.
Last edited by Alan H on Thu Feb 18, 2021 8:38 am, edited 1 time in total.
Wow. Bet Mike is relieved to have it sorted. Was it running badly before ? With Mikes attention to detail I bet changing to iron bores on a B model will be a big thing for him.
Currently without a GT, but looking
2003 Yamaha Fazer 600 Blue
2020 Triumph Street Twin Red
1968 BSA Bantam Sports Red
I’m certainly pleased! And very many thanks to Alan for his above & beyond commitment to getting another GT550 pulled back from the brink I was almost ready to push mine over!
Brief recap, I bought it in 2012 as a badly running mess, sent the motor intact to SEP, who messed up with 1mm over long con rods (without telling me) and subbed out replatimg the cylinders without also sending the pistons. Even after providing 1mm base spacers (doh!) it was never happy, scuffing pistons and running noisily. A few hundred miles in, it seized on the left while I was riding it. This time I stripped the motor. Appleby did the crank using NOS rods I provided. I had the replating done with pistons sent as well. It then seemed ok but was a little noisier than I’d expected. A few hundred miles in, it became very noisy and I measured compression well down on centre. I parked it in the corner of the shed for some months.
Alan and I dismantled it this week finding a grey, scuffed centre piston and the others lightly scraped on intake side. We validated oil delivery from pump drive to emergence of oil drops in the intake throat brass tubes, so cannot explain history. Airbox was very grubby and gritty, I’d slipped up and never done a 10/10th clean on that. So we did that, and rebuilt per Alan’s post. The new top end is much quieter than any previous build & so far remains so after an hours running over three heat cycles.
Touch wood it stays that way!
Enjoy your bikes and appreciate your friends!
Some of them run fed only with toast & jam!
Mike
My 550B is languishing in bits in the garage, I've been considering a replate/pistons/rings etc but the cost is looking prohibitive, if its not a state secret could I ask who made the liners and did the work? and if possible the cost?
Brilliant round up Mike, and very informative for fellow GT550 owners. Lets hope its now sorted for the long term. I am about to post about me GT550 woes
Harry
Currently without a GT, but looking
2003 Yamaha Fazer 600 Blue
2020 Triumph Street Twin Red
1968 BSA Bantam Sports Red
now it's time to put some mlies and smiles on it Mike. 
