Topic: StrongPerf 550 project! CARB / Pods / battery / tank / tuning thread with pics

[StrongPerf]

You're battling with the famous 500 flat spot....it was still there on the 650, as I recall.
One suggestion comes to mind, as I didn't see it in the posts I've had time to read:

Have you tried running with the airbox in place, but without the foam filter? (Like, with a paper or K&N or no filter at all?)

And, a comment: the 500/550 bikes always suffered a flat spot in the 4000-5000 RPM range for several additive reasons:
1. Long intake tract. This improved bottom end, but impedes the transition to high end until ramcharging occurs from the length, hence the "spitback" range, as we used to call it.
2. Poor construction of the intake tract right over the intake valve(s). This area needs a pocket, which reduces the flat spot noticeably.
3. Spark advancer rates never matched the cam on these bikes. To smooth out the flat spot for our lady riders, we used to cut off 1/2 to 1 coil on each spring: for the hotrodder we installed softer springs. Either one blended the flat spot into either an extension of the low end (cutting springs) or started the HP sooner (soft springs). Another option was to alter the cam timing, which accomplished the same thing: move it forward to improve midrange at the cost of 1 HP or so up high, or move it later to push the spitback range up toward the  ramcharging end of the intake dynamics. This made it a Johnny-come-lately on the HP, but made an extra 1 HP or so at 8500 RPM, with power starting just over 6000 RPM.  The change was 3-5 degrees on the cam sprocket.

Make sure on those carbs: the air passage from the air horn to the emulsifier tubes must be VERY clean. These collect tiny particles over the years, and are invisible to the user: this is the little brass fitting in the air horn that has a tiny hole in it: that hole goes thru the body to the emulsifier tube, adjacent to the needle jet, right at its base. Even a 25% blockage can cause uneven carb performance. I clean these with mechanic's wire and brake cleaner, then compressed air. Gotta disassemble the carbs to get at them (even remove the needle jet), but I've found it worth the effort, and do it to every bike I rebuild.

Hondaman - Thanks for your input.       It acted the same way even with the pod filters.

I'll check those air passages real good. I'll also do a sync, compression test, leakdown and such just to make sure everything is right. I'll go over everything.

I just figured I should at least have even looking spark plugs to start with before doing the port and cam work. Agian, I'll check everything.

Looks like I've got lots to do this weekend!

Again TT/Hondaman, Thanks for you help. I'll keep you posted.

[StrongPerf]

Thanks for all the help guys. I need to remember to check the easy stuff first. I spend 4 hours pulling the carbs and going through them again. All seemed good. I got a machinist friend to make a 14mm to 12mm adapter for my compression tester and leakdown tester.

Cylinder #1 - 105psi  Cylinder #2 - 55psi  Cylinder #3 - 95psi  Cylinder #4 - 110psi.

Cylinder #2 - 20% leakage Cylinder #4 - 8% leakage.

It's the rings not sealing.

Looks like it's time to start a motor building thread.

I know the cylinders should be fairly equal. I'm wondering what psi I should see for a well sealed up stock 550.

Thanks

[TwoTired]

The actual PSI reading is dependent on the compression ratio (assuming no leaks).
Many compression testers add volume to the combustion chamber and change the compression ratio.
Therefore, compression numbers vary depending on the tester you use.
The 550 combustion chamber is 15.2cc.  How much volume does your tester add?

To differentiate between ring leakage and valve leakage, a small amount of oil is added to aid ring seal.  Valve leakage won't be significantly changed with a viscous fluid, but rings will.

A leak down tester is supplied pressure from an external compressor.  So, tester added volume is unimportant for the test.  Merely what the chamber holds at TDC vs. what is supplied.  In a perfect world the numbers on the two gauges would be the same.  The difference in the two gauges relates to how fast compression is lost.  If bad enough, you can hear where the pressure escapes.  And, where the sound comes from tells you what is leaking.

Cheers,

[StrongPerf]

Guess I didn't explain enough. I did a leak down test. I got 18% leakage from #2 (the worst cylinder) and 8% from #4 (the best). It was leaking at the rings. Oil did stop it.

The funny thing is #4 tested best but was the spark plug with the shiny stuff (oil deposits).

Guess I'm looking at a ring job.

All this was done cold. I will re-test warm when I get a little time...

Thanks

[HondaMan]

Guess I didn't explain enough. I did a leak down test. I got 18% leakage from #2 (the worst cylinder) and 8% from #4 (the best). It was leaking at the rings. Oil did stop it.

The funny thing is #4 tested best but was the spark plug with the shiny stuff (oil deposits).

Guess I'm looking at a ring job.

All this was done cold. I will re-test warm when I get a little time...

Thanks

One thing to keep in mind on these engines: the metals used in them was, um, less than the best. As a result, the cylinders became shapes other than round in about 10,000 miles in most cases. Mostly, new rings did not fix this problem of sealing when this occurred, but boring to first oversize permanently fixed it, as the cylinders had cured, and the new bores would not reshape. The standard racer's setup on these bikes was to get one, ride it 5k-10k miles, bore to at least 1 oversize (.25mm/.010") and gain back as much as 10% HP. On my 750, for example, at first oversize, it picked up a little over 5 HP.

As long as you're taking it apart...first or second oversize, and how about a port job, which really wakes up the 500/550? If you match the piston weights in the process, the smoothness afterward can become like an electric motor on those bikes. My brother called it the "Gold Wing effect". 

[StrongPerf]

Guess I didn't explain enough. I did a leak down test. I got 18% leakage from #2 (the worst cylinder) and 8% from #4 (the best). It was leaking at the rings. Oil did stop it.

The funny thing is #4 tested best but was the spark plug with the shiny stuff (oil deposits).

Guess I'm looking at a ring job.

All this was done cold. I will re-test warm when I get a little time...

Thanks

One thing to keep in mind on these engines: the metals used in them was, um, less than the best. As a result, the cylinders became shapes other than round in about 10,000 miles in most cases. Mostly, new rings did not fix this problem of sealing when this occurred, but boring to first oversize permanently fixed it, as the cylinders had cured, and the new bores would not reshape. The standard racer's setup on these bikes was to get one, ride it 5k-10k miles, bore to at least 1 oversize (.25mm/.010") and gain back as much as 10% HP. On my 750, for example, at first oversize, it picked up a little over 5 HP.

As long as you're taking it apart...first or second oversize, and how about a port job, which really wakes up the 500/550? If you match the piston weights in the process, the smoothness afterward can become like an electric motor on those bikes. My brother called it the "Gold Wing effect". 

That's the plan. I'm looking at the 555big bore kit for the 500 on e-bay. I think it's 2nd oversize (58.95mm measured at the skirt) for the 550 and comes with rings and gaskets.

I think not spending more for the 605 kit (they've been like $400 when you can find them) and not having to spend money to put bigger sleeves in is probably what I need to do right now. I'd love to splurge and go with the 605 but no one would be getting Christmas presents...

I also have a set of 62mm KZ650 pistons but I was saving them for that "someday" CB650 hoped up motor. Also they are very hard to find standard size rings.

I will be porting the head and putting in the 650 cam regardless.

I'll start a motor rebuild thread as soon as I tear into it. Looking forward to inputs!

Thanks

[StrongPerf]

I'm moving on to rebuilding the motor and painting the bike. I've made progress with the Cafe seat. I just thought I'd post a couple of pictures of the current look before it transforms again.

[cben750f0]

man thats a great looking bike M8, and i looooooove that singarm


wot color you paintin it?, Matt black with some sort of pin stripe or GT stripes would look awesome...


good luck with it all


peace

[StrongPerf]

wot color you paintin it?, Matt black with some sort of pin stripe or GT stripes would look awesome...

It sure would look good but would be too easy.

I think I'll keep it a surprise. I will say that I have 2 options and I might go with both.