Topic: Blue K2 750 "Louisville Bike" tune a guitar, tuna fish, I can tune old Louis?

[Don R]

 The bike that refuses to be fixed. Stock air box, Hooker 4-2 header.
 It runs good after it gets some rpm's but lousy at idle. Things I've tried, cleaning carbs, multiple times, multiple carbs racks. Points, checked, gapped, checked dwell, timing good, advancer springs trimmed, spark good, plugs new, caps new, fuel new, air filter new, leakdown 3 to 4% cold, valve lash checked, one corrected, all rockers rocking, float levels set, exhaust pipes not plugged, tank cleaned, petcock rebuilt, new fuel lines, carb rubbers appear to be OK, no rpm change when spraying them with flammable carb cleaner, new tested battery. A competent builder did a big bore kit in the 70's or 80's, I'm wondering about the cam timing.
 I'm trying to get my brother to just try riding it for a while. It has sat unridden multiple times and I'm sick of working on it. I put all of my chrome parts on it and aluminum rims on new BT45's.
 It's entirely possible it was sold to us with this issue, this is as good as it has run since I've been around it.
 Ideas that don't include me pulling the engine? Because if it comes to it, I think I'll cut the frame first and weld in a kit.

[M 750K6]

Does it have the correct pilot jets for a big bore kit?

[HondaMan]

Does sound cam-ish?
Can you guesstimate the intake valve opening by watching #1 or #4 rocker while slowly  kicking the engine over? As soon as they start to move (I usually stick a 0.001" feeler in there to tell when it snugs up and can't be pulled out, calling that "close to intake opening" time. Then I take a look at the timing plate/spark advancer marks to estimate when the intake is opening. If it is sooner than about 15 degrees BTDC, it probably won't idle without help, in my experience.

[newday777]

Did you do a vacuum sync Don?

[Don R]

 I did a bench synch, I'd think it would need to idle better for a vacuum synch.

 Thanks Mark, it does sound cammy, like a top fueler! After 2500 rpm, it runs pretty good. I was wondering how to check the cam timing with the cover on. Now I have a clue.

 I have frame connectors now and it's getting close to Sawzall time. It's a non-stock K2 with a K1# engine anyway and a replacement frame stamped by me. 
 I told my brother it's haunted. The PO got hurt on it and the leg wound never healed, the engine builder passed from ALS a few years after. He remembered building it, but the details were lost in the blur of 836 kits he was putting on back then. He told me they actually bought 836 kits faster than they could make them.

[newday777]

I just did a vacuum sync on a K1 yesterday after a ultrasonic cleaning and refresh. They were way off to begin with and was popping back through the carbs, wouldn't idle well.
All is better now.

[Don R]

 Good to know, I may try that too.

[Don R]

  I worked on old Blue Louey again today, we re-checked the point gap and then dwell, I still need to re-check the timing since I adjusted dwell to 23*. It was a couple less. #1 and #2 are pipes are colder when idling and I spray water on them. I adjusted the floats and re-checked them with clear tube bowls. 1 was maybe a tiny bit low and 2 was a tiny amount high both check fine now. 3 and 4 tomorrow.
 I did Hondaman's cam timing check and it looks good.
 The right side backfired while starting a couple times, there's a clue, the low speed rumble is on the right side hooker header. #3 is really hot when I spray water on it, #4 less hot but more than 1 and 2.
  I'm trying to not get careless but this old dog is wearing me out. My brother wants to ride it to a show this coming weekend.
  Tomorrow I'll check the running timing, look at the plugs and if there's no joy by then I'll finish cleaning another nice set of carbs to try.

[HondaMan]

Umm...about those clamps that hold the carbs in the hoses: if they have been off-on a numbers of times, they may not be closing all the way tightly now. Maybe look at the screw-head seats on the clamps to see if they are pulling thru the bands? I have made many a flat-sided #6 washer to fill in and flatten those worked-on clamps before. These often caused one-cylinder-hot-another-cold type running, despite vacuum sync and timing checks.

[Don R]

  Thanks Mark, I checked and found at least one clamp that was bottomed out. We drug a nice appearing rack of carbs out of the parts stash, we're going to clean them and test the float valves while they are on the bench, the float levels look good static. There's also a huge collection of stock used clamps so we'll pick out a good set and inspect the rubbers.
 40 pilot jets and 120 mains on the set getting cleaned, I'll check the parts box for smaller jets. It has a big bore kit, stock air filter and a sweet 4-2 hooker header that isn't plugged up. Cam still unknown, not too many guys around here did a cam swap but you never know. The PO didn't brag about a cam when we bought it.
 

[Don R]

  While it was cold this am I re-checked the lash, .002 intake, .003 exhaust.  Timing, checked and 2-3 were fine tuned. Dwell, re-checked and still at 23*. I have a box full of test spark plugs lol. I tried swapping a set.
 I lowered the oil level, it was high after I added some Rislone thinking it had a sticky valve. I'll change that back out before riding any distance. I sprayed some flammable carb cleaner around the carb rubbers (no change) and checked the old clamps.
 I got out the morgan carbtune and get nearly no vacuum readings unless I rev it and let off. #2 is the most responsive. This is with the stock airbox and filter and the Morgan vacuum lines have the factory restrictors in them.
  Edit: on a dial gauge with the Morgan snubber in line #1 reads 10" vac at 2,000 rpm, swings wildly between 0 and 15" at 1500 rpm and lower.
  The end carbs made 165/170 psi cranking compression, the middle ones 155 psi.

[Don R]

   How can it make that much compression, leak down 3-4% and yet pull very little vacuum?

[newday777]

This is my Carbtune on a K0 motor(in a K8 frame) the other day, at 1300-1400 rpm.
I used the 5mm brass tube adapters with orings and nuts, to seal to the carb ports that I've had @ 10 years instead of shorties that came with a Morgan.

[Don R]

  That's what I was hoping to see Stu. My brother asked when it makes that much compression, but very little vacuum where does the air come from? 
  I think I need to see the cam. If you're squeamish, don't look at what happens next. It involves frame connectors.

[HondaMan]

If you're squeamish, don't look at what happens next. It involves frame connectors.

OHH, the humanity...!

[Mark1976]

  That's what I was hoping to see Stu. My brother asked when it makes that much compression, but very little vacuum where does the air come from? 
  I think I need to see the cam. If you're squeamish, don't look at what happens next. It involves frame connectors.

   Why don't you put a degree wheel and dial indicator on it and see what kind of numbers you come up with. It does sound as though you may have a bit of extra duration in there.

[M 750K6]

Just a thought, as it's measuring vacuum in the carb. Is the idle screw adjusted down, are your slides fully down?

Unlikely all 4 would be bad, but are you certain the seal at the top of the carbs are good and inlet rubber boots are good.

[Don R]

 It's a new carbtune, I wondered if the tubes were sticky but at this point, I doubt everything that I thought I knew. I can't even make an intelligent theory.
   I might raise the idle until the slides read, I did get one and two to react the same to revving and letting off.
  Maybe if I keep after it, they will at least all react the same and things would begin to make sense to me. I did unscrew a threaded plastic vacuum hose adapter and can move the carbtune by applying suction to the hose, so it can respond to vacuum.

[newday777]

If you have a Mighty vac you can test each tube to verify the Morgan is balanced with each tube using the same vac pull amount.

[Don R]

 Good point. I'll do that. I think there are tee's left over from when I buy the multi-pack.

[newday777]

No tee needed to individual test each tube.

[Don R]

 I went out to leave for a ride on the GS1100 but old Louis was calling me. I started it, as usual  it sounded good for a few seconds then there was a noticeable exhaust pulse on the right side, the #3 header was hotter than any other pipe when spraying water on it. Either lean or rich.
  I dropped the #3 and 4 bowls, checked the float levels again with the clear tubes. Those looked good so I pulled the jets again. When looking into the pilot jets #3 let more light through than #4, so I got out the guitar string pilot cleaner. It normally only goes in until the size of the wire changes, but this one would take the string all of the way through. I checked it with a torch tip cleaner and the same thing happened, when the larger OD got there all other jets stopped except that one. Still #120 and #40.
 AHA! Drilled pilot jet. Some #$'er got me.
 I also made an aluminum shim for one carb clamp that was bottomed out and now it tightens with a bit of threads left. Now suddenly the carbtune sees a little vacuum just above idle so I got the carbs balanced, the vac is still low but it idles now.
 Sometimes it's a lot of little things that all add up. Film at 11.
 With any luck we can both ride to our final car show Sunday.

[Don R]

 This, finally.

[M 750K6]

Don,
Admire your patience. Hope I'm not raining on your parade! The service manual says 16 to 20 cmHg @ 800-1,000rpm. TBH, I don't know how critical that reading requirement is, versus just having them all even. When I synch'd mine, using the same Carbtune tool, I had one carb in that range and set the others to it. It moved a little as the others got near, but I felt Iwas lucky, as they ended up close and in that range.

[Tracksnblades1]

Don,
Admire your patience. Hope I'm not raining on your parade! The service manual says 16 to 20 cmHg @ 800-1,000rpm. TBH, I don't know how critical that reading requirement is, versus just having them all even. When I synch'd mine, using the same Carbtune tool, I had one carb in that range and set the others to it. It moved a little as the others got near, but I felt Iwas lucky, as they ended up close and in that range.

K6,

Just wondering,rhetorically, after reading all the post in the entire thread, what the service manual says the cmHg reading for a cycle X (xxx4) camshaft would be @ 800-1000rpms.  Supposably the biggest, baddest of all cams for a sohccb750…?
😏

[Don R]

  No worries, I know it's fubared, it idles beautifully. Still runs like crap though, maybe even worse. At least before it would run over 2500 rpm OK, now it sucks at everything over idle.
  I need to see the cam timing next, otherwise swapping known good parts (engine) from another bike might be the answer.
  I'm done playing with it, my brother gave me the title back lol. 

[Don R]

  This just in, bad spark plug. It must have died during the test ride. It was a Denso. I also re-adjusted the cam chain tensioner.
  I think the drilled jet ruined the plug, that's the cylinder that would come in and go back out. I heated the plug with a torch and wire brushed it, no luck. Trash can. i put in a slightly used NGK and it's running fine.

 Everything I find only makes it a few % better. I really need to up my game as far as thoroughness.