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

[Tintop]

That's x2 for getting it on a dyno.  In Toronto you have - Z1cycletech / Pro6cycle / Riders Choice.  There's also Mackie's HD in Whitby.

[akabek]

When I bought the bike it already had the CR29 carbs and trust me I have thought about picking up stock carbs.  I have never driven a stock CB550 so I have nothing to compare against.  I have read and heard people say different things about CR carbs but in some cases I have over come those issues.  I was told you have to roll on the throttle and that CR carbs cannot handle an abrupt WOT.  With the right jetting a quick WOT is not an issue.  Yesterday with new plugs I was able to get the bike to idle at a lower RPM so I know it is possible.  I am baffled why my plugs went from white to black and no gradual color changes as I turn in the mixture screw.

The carb is staying on the bike so I determined to get it dialed in.  Once I get to a point of where I like the jetting I may take it in for a dyno run.  I know of some shops with Dynos in Toronto but I don't know if they will touch a vintage bike for fine tuning. 

I have a lot of time and money in the bike and I want to see it through.  Carbs have always been why weak point so this is my chance to get over that hump.

[akabek]

That's x2 for getting it on a dyno.  In Toronto you have - Z1cycletech / Pro6cycle / Riders Choice.  There's also Mackie's HD in Whitby.

Z1 is closest to me but before I take it in I need to replace the clutch and get it reasonably dialed in.  Will the shops or dyno report be able to translate what needs to change with the jetting/needles etc?  Would my best bet be to find a shop with a dyno and a mechanic familiar with carburetors?  I know all three shop from my trackdays but I don't know if they know vintage carb tuning....

[Tintop]

I'd just call them and ask, but the CR's aren't exactly vintage, like the bike.   As for what you can expect, depends on how much time ($'s) you want to spend, and how many parts you have to swap in/out.  A couple of pulls to get an baseline A/F would at least point to where the issues are.

[akabek]

I am not planning to race the bike so I will hold off on the dyno for now.

Before I mess with the carbs any more I will redo the clutch.  Than I am going to start at square one and double check I have the right main jet and work my way back.  I have a feeling I may be lean on the main jet but I will know more when the clutch is working as it should.

[Retro Rocket]

I am not planning to race the bike so I will hold off on the dyno for now.

Before I mess with the carbs any more I will redo the clutch.  Than I am going to start at square one and double check I have the right main jet and work my way back.  I have a feeling I may be lean on the main jet but I will know more when the clutch is working as it should.

Regardless of whether you are racing or not, the dyno will tell you which direction you need to go in to get your tune right, trial and error can be quite frustrating...

  A couple of pulls to get an baseline A/F would at least point to where the issues are.

+1

[akabek]

Regardless of whether you are racing or not, the dyno will tell you which direction you need to go in to get your tune right, trial and error can be quite frustrating...
[/quote]

Fair enough.  I get set it up to what I "think" is right and than take it in for a dyno run.

[akabek]

I just installed a new Barnett clutch and took a spin on the highway.  The slipping at high RPM is gone now.  I have a question on adjusting the clutch.  On the right case cover there is an adjusting screw and locking nut.  The instructions say to turn it counter clockwise until it stops and than turn is back 1/4 turn.  When I do that the clutch engages within 1/2" on the clutch lever.  Where do I make the adjust to change when the clutch engages?

When I came back from the ride I pulled the plugs and two were partially white and two where a little rich so they seem to be close now.  The bike pulls well in the mid section but tapers off when it starts getting into the high RPM range.  At full throttle if I ease up a small amount it hesitates.  Does this mean I should try a 122 jet?  I have a 120 in there now. 

[akabek]

I went ahead and increased the jets to 122 mains and went on the highway.  The mid acceleration was still great but the bike did not want to go beyond 8K RPM.  My understanding is from 3/4 and up that is the main jet so dropping the needle clip will probably not help.  Am I correct to assume I am lean on the main jet?

[turboguzzi]

Branden, you are confusing our friend.... hes running a big bore 550/600, not a 836, so 120-125 should be his range

when i mounted the CR29 on my 810, they indeed worked better with a 115 main, the bigger displacement kicks up flow/vacuum, so you need a smaller jet.

his smaller motor will need bigger jets that yours.

akabek, sort out your main jet/WOT setting and only then proceed to needle hieght

[brandEn]

sorry, just trying to help. I will stay outta this one.

[turboguzzi]

akabek, are you running stacks? could help if you do

if you have the time (and with CRs changing mains is a doodle, even on the road) would do a few WOT runs, not caring about mid range, just top end to sort your main jet size. after you find what main gives best top revs, move down to mid range playing with the needle height.

[akabek]

akabek, are you running stacks? could help if you do

if you have the time (and with CRs changing mains is a doodle, even on the road) would do a few WOT runs, not caring about mid range, just top end to sort your main jet size. after you find what main gives best top revs, move down to mid range playing with the needle height.

My engine set up is in my first post.  I am running Steel Dragon stacks with BBR filters and a CB650 cam.  My plan is as you said to just lock in my mains.  Luckly the highway is only a few minutes out my door. 

Yesterday I changed my mains from 120 to 122 and the bike would not accelerate past 8K RPM WOT.  Behind the exhaust pipe was getting black and with the sluggish WOT I must be rich.  Then I put in 118s but it started to rain so tonight I will see how they work.

I use to removed the carbs to change the jetting but now I just leave them on the bike.  It takes 30 mins to change the jets but I have a good system going now.

[turboguzzi]

wouldnt be surprised if those mesh filters (if that's what they are ) are playing havoc with your jetting, a bit like pods but worse   very little volume behind them and not much filtering surface.

for science sake would do a run without them. try also without the stacks. as they are not the original keihin ones, wouldnt be surprised if they do more harm than good.

[akabek]

wouldnt be surprised if those mesh filters (if that's what they are ) are playing havoc with your jetting, a bit like pods but worse   very little volume behind them and not much filtering surface.

for science sake would do a run without them. try also without the stacks. as they are not the original keihin ones, wouldnt be surprised if they do more harm than good.

I do have the original stacks but for street use I want some filtering.  I originally planned on pods but there was no space.   I am going to try what I have on there now and see how it goes.

[Tintop]

+1 with TG's observation regarding the filters.  Current (ie F1) thinking is you should have a minimum distance from the stack bell mouth to the inside back of the filter no less than the throat/venturi dia.  Eg. with 29mm carbs you should have at least 29/30mm clearence (more is better).

[akabek]

Just to add to the mess the after market stacks already have a single layer filter mesh built into the base.  I added the BBR filter to the bell mouth so there is more going on in the equation.  I have no room for pods so I went with these stacks for looks and added filters for "some" protection.

Is my best course of action to jet the carbs with the original stacks and when I am done put the aftermarket stuff back on?  I assume this will leave me a little rich which is a good thing.

[turboguzzi]

just try and do a run with stock stacks, 120 main and 8 needle in mid position. if things get better, then you know where the problems was

[bwaller]

I hate to add another negative, but some stacks just don't work. With the CR stacks how much room from the frame rail to the bellmouth, can't be much different than mine, I use dual sock foam filters.

At some point in your testing try the three different options in one outing just to see if there is a difference.
1) with your stacks
2) no stacks
3) CR stacks

I see TG suggested something first, we're trying to get you to remove those stacks.

[akabek]

I hate to add another negative, but some stacks just don't work. With the CR stacks how much room from the frame rail to the bellmouth, can't be much different than mine, I use dual sock foam filters.

At some point in your testing try the three different options in one outing just to see if there is a difference.
1) with your stacks
2) no stacks
3) CR stacks

I see TG suggested something first, we're trying to get you to remove those stacks.

I get it.  My current setup is not ideal especially with two sets of wire mesh.  I don't care which stacks I use but I want some sort of filter protection as this is a street bike but not an every day rider.   Which sock filters did you use?

[Retro Rocket]

The CR stacks are also a far better design than the steel dragon "built for looks" stacks. Not being a smart ass but look aat the CR stacks and the SD stacks and see the difference in the bell mouths, the CR's are designed to flow properly, the SD are for looks....

[akabek]

The CR stacks are also a far better design than the steel dragon "built for looks" stacks. Not being a smart ass but look aat the CR stacks and the SD stacks and see the difference in the bell mouths, the CR's are designed to flow properly, the SD are for looks....

I am good with going back to CR stacks but I need some kind of filter on their for street use....

[Retro Rocket]

The CR stacks are also a far better design than the steel dragon "built for looks" stacks. Not being a smart ass but look aat the CR stacks and the SD stacks and see the difference in the bell mouths, the CR's are designed to flow properly, the SD are for looks....

I need some kind of filter on their for street use....

I hate to add another negative, but some stacks just don't work. With the CR stacks how much room from the frame rail to the bellmouth, can't be much different than mine, I USE DUAL SOCK FOAM FILTERS.

Brents bike is a successful race bike, ask him for details on his filters...

[akabek]

You guys think your so smart

Leaving everything as is: steel dragon stacks, 118, 65, YY7 (5th clip) I decide to just remove the BBR filters.  It really goes to show how every little change can make a big difference.  I was almost able to hit redline before the bike bogged which tells me I need the 120 mains back in again.  On top of that the bike was really sounding good and pulling more in the high range.

just try and do a run with stock stacks, 120 main and 8 needle in mid position.

I would say you are right on the money.  The only thing is I do want some sort of filter on my stacks.  So bwaller what do you recommend?

[bwaller]

My filters are from ITG. www.itgfilters.net.  Have a look around there are other options apart from the ones I use. The trick is to have as much room between the bellmouth and the back of the inside of the filter. I think I have 45mm, not a lot but space is tight as you know. I forget what the CR stacks are like but the folks at ITG can surely suggest something.

It is with certainty that some think I'm nuts too for using these on a race bike and I'll bet there's a hp or two to be found running without them. However I have seen the strangest things ingested into an engine with open carbs.

Truth is your screens will keep low flying birds out, but the damaging material will be sucked right through. I'm with you though, use some sort of filter.

I'm sorry man you probably feel like we're picking on you, not the case. TG's latest suggestion on jetting awaits!