Potential Group Purchase - Wiseco GS650 741cc pistons

[frankenwabbit]

Chuck78....I'd be up for getting in on a mls gasket once someone here has crunched the numbers.

[Chuck78]

Has anyone got their pistons installed for a torqued mockup of the cylinders to measure for deck height?
I was thinking I'd order 4 or 5 .043" or so thick MLS gaskets from gasketstogo.com, maybe 1 or 2 .030". Old Colt, have you mocked up yours yet?

I'll have to double check on the thicknesses available from gasketstogo.com but I think those guesses were close to what is available.

[Chuck78]

Yes, do not mess around with trying to fine-tune the syncnonzation or idle, you are wasting your chances to get the rings broken in properly for the best seal and compression. Do as much research as you can for a good ballpark Main Jet size, needle jets, jet needle and needle clip position, and go out for some medium hard pulls doing the acceleration deceleration thing a dozen times or so. And don't run fancy oil during that break-in period.

[tkent02]

Awesome info on break in procedure Etc guys!!

I have some questions though.

how long can I run the engine to sync carbs and sort jetting before it will glaze the cylinders?

Do I get it as close as possible on the bench them sort it after the run in period?

Smooth idle and perfect synchronization isn't all that important when you're breaking in an engine, since you should be going on and off the throttle anyway. Full open or full closed, synch doesn't matter. Where poor synchronization sucks is trying to ride gently and smoothly in traffic or on a slow or slippery road, or anywhere else you want smooth throttle response at low power.

I'd bench synch them as well as I could and ride the Hell out of it, save the fine tuning for later. Been doing this on my 550/675, after a decent bench synch it ran fairly well anyway, the synch isn't very far off. Got to get into the fine tuning part soon, my jetting is a little bit off but the compression is good.

Andy, the pistons arrived safely in the UK, got clobbered with a customs charge though...Very happy with them, thanks for your help

[Nessism]

Awesome info on break in procedure Etc guys!!

I have some questions though.

how long can I run the engine to sync carbs and sort jetting before it will glaze the cylinders?

Do I get it as close as possible on the bench them sort it after the run in period?

Put a big fan in front of the engine before doing the vacuum sync job and don't worry about getting it perfect at first. Just get them reasonably close and go ride. You will be fine. Cylinders don't glaze over that easily.

Awesome info on break in procedure Etc guys!!

I have some questions though.

how long can I run the engine to sync carbs and sort jetting before it will glaze the cylinders?

Do I get it as close as possible on the bench them sort it after the run in period?

I would first have the piston skirt clearance checked. If they were tight that could have been an issue and is real easy to remedy during your build. Eather way all of us need to confirm the piston clearance and ring end gaps.
It is hard to diagnose an overheating when you only have a small piece of the original but mixture and timing are the first two external items you will address.

Ok I bought my cylinders used from a guy on here that tried this build with some normal 750 pistons. He was having trouble with his engine over heating though. Should I do anything with my cylinder to help prep them? I have not done anything to them since I bought them.

Eventually I plan to sent my head off to a good machine shop about 45 mins from where I live and have them make sure the valves are in good shape.

Ed, you seem to write faster than me, but then I have been working up on the roof.

Haven't had anything bored and honed in decades, except for using a ball hone myself to put new rings in a used cylinder. If I get a cylinder bored for these pistons will they hone it properly?

Boring a cylinder is a two step operation in which the final part of the job is honing to final size. being you can not size a cylinder with any flex hone whoever does the job will have a proper hone and this day and age I would sure hope they have finer grit stones than were used way back in the days of leaded fuel and 2mm wide rings.
A race engine shop that can work down in our cylinders smaller bores of a bike shop that caters to engine work. Not necessarily a Harley shop since they are tooled differently than these engines need.

[Nessism]

A machine shop with experience boring/honing motorcycle cylinders is ideal. The liners in air cooled cylinder blocks can spin if too much pressure is used either during honing or boring. Machine shop guys familiar with air cooled engines should know this sort of stuff (hopefully).

[Chuck78]

Find a good quality reputable machine shop, especially one that does hot rod engines or air-cooled old Volkswagens.

Give them your pistons. You may want to hang onto the clips pins and rings so they don't get lost. Have them measure each piston very precisely, as there is often a very slight variation in diameter on the pistons, & Wiseco is known for this... Then have them finish hone based on the piston to wall clearance spec that is printed on the Wiseco packaging. Make sure they measure all if the pistons precidely, and if any variation, adjust clearance specs for each cylinder for the final honed bore size. This will require marking the cylinders 1 through 4 and marking corresponding pistons appropriately for the hole that was sized precisely for that piston.

I have 12 of these babies, so if I can turn up a micrometer big enough to measure the pistons, I will compare them myself. I also need to get a small digital scale and adjust the weights of the pistons until they are all identical, & possibly remove a slight bit of material from strategic areas with a dremel type of cable driven grinder until they are closer to OEM piston weight. This will balance it out better and help it spin the engine up faster.

[tkent02]

Haven't had anything bored and honed in decades, except for using a ball hone myself to put new rings in a used cylinder. If I get a cylinder bored for these pistons will they hone it properly? Ready to throw it together as is or will it still require some honing? How can I find the best place in town to do it right? Same question with heads, how can I find the best shop to do it right? Nothing too fancy, just a nice tight valve job, maybe a little porting.

[Chuck78]

^^^^
EXCELLENT INFP, good to know. Thanks Ed & Charlie.