Pinging, popping GT550B

[tz375]

Normally yes, but in this case it sounded potentially more serious and when the pistons were seen sticking up above the barrels, that became a priority to get the pistons and barrels in the correct relationship to each other first.

Then test and see if the problem is still there and if so adjust timing or fueling to suit, but it has to be mechanically sound first.

[jeff kushner]

"full rebuild including crank, rods, replating the nikasil cylinders (Euro ported bike) and Suzuki pistons/rings. Engine was done at great cost by SEP Engineering UK"


I re-read this thread and I guess I had skipped over the obvious the first time.

It just seems odd that an accomplished mechanic would pay to have an engine built, then go through all this work and discussion having not once called the actual builder? I'm not knocking the owner but doesn't picking up the phone and calling the guy who you have sent a check to and assembled your engine seem like one of the very first steps? You paid, evidently, a lot of cash to have this engine built and it doesn't run correctly yet instead of calling them to decipher the issues, you take it apart? I would think that SEP would jump at the chance to stand behind their work.

I'm just saying....

Good luck,

jeff

[tz375]

If SEP chose to fit a longer rod and then assembled the motor without checking deck height, then they deserve to be publicly chastised and they should be making good their substandard work.

Didn't they screw up that CBX motor for Motorcycle mechanics years ago by not checking something? At first they though it was glass beads but later found it was something else odd that SEP should arguably have spotted.

[yeadon_m]

Jeff,

Kind of you to credit me as accomplished but I'm more a careful student than knowledgeable! The motor arrived complete with cylinders mounted but not bolted down, and head on over protective wrapping along with a gasket set. That made sense as it was easier to put the motor back without cylinders on then finish it up in the frame. That - plus ability to make observations and ask questions (I am a professional scientist, but I'm not an engineer) - is about the limit of my abilities

The thread started as you'll see with me fussing over banging and popping. That led me to go check things I'd not appreciated as potentially important. Without the post and helpful replies, I'd still be mucking about with carbs and timing.

Over the last couple of days I've now assembled enough insights from others plus own observations to have an informed discussion with the builder. The new info from good people here will help me have the right discussion and had I done that before posting I think I'd have been post as to what to say to them - its banging and popping isn't very helpful. I'm in touch with them and if time permits I'll speak with them tomorrow.

I need them to help with fix to piston over-topping and also get to a resolution on cylinder clearances.

I'll post back in due course! I have full faith we'll get there and they have been good in the past with my GT380B, which came and remains sweet as a nut years later.

Cheers!
Mike

[Ivan]

I know this from my own experience from tuning a 1976 GT550 that was brought to me by Paul Miller (one of his personal bikes)

The air screw settings were between 1/2 & 3/4 turns out with the stock pilot jets... anything more was popping and pinging at small throttle openings.

A larger pilot jet created other problems.... stock pilots at the above settings gave best driveability.

Just throwing this out there...

Good luck,

Ivan