Topic: CB550 - CR29s is this the best it gets? Will CR26s be better street carbs?

[Retro Rocket]

Thats fair enough TG but, I know of a lot of Dyna's that work fine and the problems he's been having have been fuel related..

So I have my carbs running great right through each gear but the problem is at idle.  It does not want to idle below 2K and it is running rich.

Try another ignition or put the old points back in and see,  from everything stated here it seems to be carb related. I have no doubt there was a period where Dyna made some bad ignitions, although, none of them were running well except at idle that I have read and a fair proportion were damaged by poor fitment. Was the ignition working well before the rebuild..? Are the 29's a bit big for the 550..?  I know of plenty of 750's wearing 29's, not many 550's. Are any of the other 550 racers running CR29's.... Just trying to help...  Remember, he did say it was running rich....

[turboguzzi]

yep, told him 29 are on the large side for a street 50-600,

that said, i raced a 500/4 with CR29, perfect, but never cared for what happens under 5000 rpm

breaking up at high rpm / WOT is just typical to ignition issues

Akabek, maybe try running less spark plug electrode gap? if igniton is a bit weak, it could help

[akabek]

I may not have an ignition problem.  I was just wondering if the Pamco unit is more reliable. 

With different jettings I have had the low end working great and with other setups great mid to high.  I just need to get the jetting balanced out right through the range.  I have gone back to square one finding the proper mains now that I changed my stacks.  My other issue is I have a Acewell digital tach and I am not confident with the accuracy so I am going with feel and sound.  I should have kept with the analog tach and speedo.

[akabek]

Current jetting: main 122, pilot 72, needle YY8 in 4th
Back to square one checking my mains....I pinned the throttle topped out in 5th gear and when I pulled the plugs the ceramics were white and the ground electrode was grey.  I would say I am running a little lean.  I will increase my mains to 125 and since I have the socks I will treat them and install them on the stacks.

[FunJimmy]

The fun doesn't seem to stop.
You must be an expert jet swap tech by now.

[akabek]

The fun doesn't seem to stop.
You must be an expert jet swap tech by now.

You bet, moving back to stock stacks made a bid difference in air flow so back to square one again.  I don't care to count how many times I have changed a jet or needle position but I am getting quick. 

125s are in so tomorrow I take a run. 

[akabek]

I did not get a chance to put the socks on but I took the bike on the highway for a WOT test.  Tonight I was running with: main 125, pilot 72, needle YY8 in 4th and unfiltered CR stacks.  I did not really warm up the bike and when I pulled out of the driveway I noticed it was bogging if I twisted the throttle too quick so I gradually rolled on the gas.  Once I rode on the highway for a couple of minutes she was pulling through the gears quite well.  My plugs must have been a little fowled at the start or it just runs better after warming up.

On the highway I took it to 5th gear WOT and shut it down rolling to the shoulder.  Unfortunately a tow truck showed up so I was only able to check one plug.  The tow truck driver was dumb founded with the bike as he never saw anything like it.  The plug ceramic is still white and the negative electrode is still gray.  On my way back I pulled over so I could take a run winding through the gears and she is running really well.  If I move the clip to 5th position will this have any effect at WOT or should I be looking at richer mains?  I assume putting the socks on will not make much of a difference.. 


 

[akabek]

I was just speaking to a friend of mine and he said it is tough reading plugs on an air cooled engine.  Once you shut the bike down and roll to a stop the engine is holding heat so by the time I removed the plugs it could be reading hotter than it was....

[akabek]

Weird clutch incident....

This is off topic but I recently changed my clutch with Barnett friction and metal plates.  I soaked the friction plates a few days before installing them.  I noticed once in while the clutch would grab unexpectedly while letting it out but tonight while on an on ramp the shifter was catch between 3rd and 4th gear as if I was in neutral.  It was not a issue getting it back into gear but this was a first experiencing this.  Any idea what may cause that?  Is it possible I did not torque down the 4 bolts holding clutch basket in position?  I could not find torque values so I just put them on snug but not too tight.

[FunJimmy]

Weird clutch incident....

This is off topic but I recently changed my clutch with Barnett friction and metal plates.  I soaked the friction plates a few days before installing them.  I noticed once in while the clutch would grab unexpectedly while letting it out but tonight while on an on ramp the shifter was catch between 3rd and 4th gear as if I was in neutral.  It was not a issue getting it back into gear but this was a first experiencing this.  Any idea what may cause that?  Is it possible I did not torque down the 4 bolts holding clutch basket in position?  I could not find torque values so I just put them on snug but not too tight.

Just a false neutral, nothing more. If they become persistent than it can be a sign of tranny issues but not typically from an occasional occurrence.

[akabek]

It was been a while but time to get back on course.

It was a pleasure meeting Tintop and Bwaller at the Shannonville VRRA event...always good to put a face to the name.

I had the bike running pretty good yesterday with 128, 75, YY8 6th position but the bike would bog at 1/4 to 1/2 if I went WOT.  Rolling it on was ok but it seems rich overall based on the dull exceleration.  I could go 78 pilots and play with the needle clip but it just seems like a rich setup.

...So I revisited my previous jettings (best jetting running without socks on the stacks) and decided to go back to the jetting just before I put the socks on: 125, 72, YY8 4th position based.  The exceleration was  crisp throughout but the top end was limited so I knew I was lean with the socks on stacks.  The upside is this gave me perspective on what exceleration can feel like.

I will go back to 128 mains but what is the proper procedure from here?  Do I drop in a pilot and play with needles and clip position or do I figure out the needle/clip and than pilot?

I want to keep my clip level around the 4th position with a smaller pilot.  I have richer YY5 and YY7 needles to try out which should allow for smaller pilots. 

[akabek]

Unbelievable but I think I have found the zone.  Tonight I ended up with 128,72,YY7 (4th pos), 240 air jets and socks on my stacks.  Now the bike bike is running smoothly through the gears.  I can crank to WOT and no bogging once the bike is warmed up.  Before I run it through it paces I am going to check valve clearances, cam chain tension and carb sync.  It even seemed to want to idle at a lower RPM.  Maybe I can get some riding in now. 

[seanbarney41]

....and then then the temperature, humidity, and barometric pressure changed

...just messin' with ya, weather shouldn't mess with your tune up too on the street

[akabek]

....and then then the temperature, humidity, and barometric pressure changed

...just messin' with ya, weather shouldn't mess with your tune up too on the street

Damn you...

Just kidding.  I know how finicky these vintage bikes are.  I just want to get a good ride in soon

[seanbarney41]

....and then then the temperature, humidity, and barometric pressure changed

...just messin' with ya, weather shouldn't mess with your tune up too on the street

Damn you...

Just kidding.  I know how finicky these vintage bikes are.  I just want to get a good ride in soon

been following along...but I am much too lazy for all that tuning.  I just go riding.  All due respect for making the efforts.

[akabek]

I hear ya.  In this case I was up to the challenge.  I hate carbs and it was time to win a battle.  Some minor tweaking and then I can take on some twisties. 

I need to find a good spot to mount the GoPro and record a run....

[FunJimmy]

I need to find a good spot to mount the GoPro and record a run....

Suction mount to the fuel tank.

[akabek]

Good idea.  I will have to pull my GoPro out and all the attachments to see what I have.  I use to mount it to my front fender or on the side of the fairing when I had a track bike.

[Kemp]

Pretty cool video Fun Jimmy, obviously you were sticking close to the posted speed limit. Wait did I hear that 572 hit 10,000 in top!!

[FunJimmy]

Pretty cool video Fun Jimmy, obviously you were sticking close to the posted speed limit. Wait did I hear that 572 hit 10,000 in top!!

That was last year Kemp.
It sound sooooo much stronger now. 

[MRieck]

Pretty cool video Fun Jimmy, obviously you were sticking close to the posted speed limit. Wait did I hear that 572 hit 10,000 in top!!

That was last year Kemp.
It sound sooooo much stronger now. 

It should.

[akabek]

The the CR29s are working well but the bike still idles over 2K RPM.  Being over carb'd my guess is it is what it is.  If I were to go back to a stock carb I assume the bike will be able to idle where it should??  Aside from idle would I notice a big difference in the performance of the bike overall?  Keep in mind this is a street bike, not a track bike.

[akabek]

Any feedback to my previous post?  Would a stock carb be a waste of money?

[turboguzzi]

i raced a few seasons with VM26s, they are actuallly 27mm ID, relatively cheap (compared to VM28s), easy to setup and bike was definitely fast. went with CR29s later, difference "might" have been at the very top end, maybe, never got around to dyno it with the CRs for a comparison. the 500/550 are so restricted in flow in the valve throat area that  i find it hard to believe that you will feel much difference in street riding.

my 0.02$

[akabek]

the 500/550 are so restricted in flow in the valve throat area that  i find it hard to believe that you will feel much difference in street riding.

my 0.02$

So it sounds like the valves are more limiting than the carbs.  I can get my hands on a complete set of carbs for $40 that I can rebuild over the winter.  It would be nice to not run so rich during idle although the bike works well at high RPM.  Maybe I will  not loose much on the top end going stock?