Cold running questions

This summer I picked up a nice looking '82 SECA 750.
I usually get verbose with all the details, but I'll try to keep this post brief.

Background:
Cleaned and serviced the carbs, adjusted the valves, new plugs and various other maintenance. Sync'd and colortuned (probably needs it again, but that's another discussion) with YICS tool

When the bike is cold I start it up and it idles beautifully. Almost never use choke and believe it or not, it will idle smoothly at about 600 (indicated) rpm when it's real cold.

Problem:
Starts up and runs great, but as soon as I try to take off, any torque load (like trying to get going in first gear) will kill it, unless I rev it over say 3k rpm. When it starts to die, if I let off the throttle, it will go back to purring nicely. Performs great over 3k rpm. After i drive 1-2 miles over 3k rpms, it runs correctly. I mean, I can pretty much drop the clutch and give it gas it it will go great. no dead or flat spots in the power-band, excellent response...runs like a well tuned bike...it's just getting going in the morning that is frustrating. Hate reving high in the neighborhood in the morning...and to make matters worse, my driveway and the first bit of road I am on is gravel/dirt, so it doesn't roll super easy.
It does seem like it tends to load up rather fast at idle when cold. Choke usually makes things worse, unless It's real cold and I use a very small amount. If i let it just idle hoping for it to warm up just right, it will carbon up bad and die.
Once warm though, all is happy.

I'll stop there and appreciate any and all input.

thanks!

 

slides sticking?

 

No, they pass the "clunk test" with flying colors.
I COMPLETELY stripped the carbs and cleaned them and inspected them. Float levels were checked as well. A couple of additional items I will mention. The bike has 4-1 exhaust (MAC mabye?) main jets are 124
I have a K&N filter in the filter box, not sure when it was last serviced...need to get a service kit or just put a paper filter in it.
A thought Chacal and I had was maybe with that filter in there plus the exhaust (Even though I am not running pod filters) the bike is flowing enough extra air that maybe it sould have been jetting up even more? I have the mixture screws pretty far out before the colortune starts showing the right color so it kind of seemed like I might have been somewhat compensating for jetting with mixture screws...
What about pilot jets? Mine are still stock I think..

Thanks!

Ok, other thoughts?

 

get it to stumble for a short distance and chop the plugs while it is stumbling.
see if you can pinpoint a cylinder.
if you are turned really far out on the idle screws, you may require more jet (main and pilot) to compensate for the transition from idle to cruise. I have a KN filter also and my screws require a little turning out now.
once you chop it and look the plugs over, chop them at 3500-4k and then at 6-6500 (midrange and powerband).
you should find the culprit then
good luck

 

I had to turn my screws almost 5 turns out as per color tune. It seemed to be running too rich so i've pulled them back a tad. The plugs have all been pretty similar for the most part, but I do need to do another plug chop(s)
It deffinately feels like it's the transition that is rough untill it's warm. I was sort of wondering (trying to remember) about the pilot, maybe if that was up a bit, that would help out sufficently? If the KN filter is flowing so much more air causing this, I'm thinking maybe it would be easier to go to a stock style filter and see if that eases up my jet issue. Performance is great, but frankly I wouldn't mind keeping things simple and going all stock. But this is how the bike came to me (and it was uber cheap and looks great, so no complaints)
it's kind of hard to keep it stumbling, it just wants to die out unless I pour the coals to it, but i'll give it a try. Thus far, my experience has show pretty carboned up plugs from cold idle and when it's running nasty. (Main reason I pulled the mixture screws back to more like 4.2- 4.5 turns...I need to do another color tune and see what I find. I never got a white color, just nothing, blue or orange)
Thanks!

 

so, it runs fine when it is warm?

 

sorry, hit submit too soon.
these carbs are very very cold-blooded machines. it shouldn't idle at 600... ever. the engine has 3 basic requirements to run: air, fuel and spark. since these carbs do not have a diaphragm to squirt fuel in, it requires vacuum to do this for you. when it is cold, it just isnt happy about putting fuel in the chamber, so it must have something to make up for it: enrichment circuits.
the bike makes very little vacuum at 600 RPM and will not get enough pull to bring in fuel without the "choke" on at least a little.

 

It runs GREAT warm.
Now, I don't know how accurate the tach is at very low rpms, but it can and has idled closer to 500 rpm than 1000 for a short while when first started. Right now i have the idle turned up a bit, but I was shocked how low it would run. I have it now so it is running more like 900 or so when first started and near 1100 when warm/hot.
All this without the choke on. Yes, I have checked the enrichment circuits, that was one of the first places I checked when I first got the bike running after working on it. They all are fully seated down, circuits were cleaned and the valves were too. All mechanical indications are that the enrichment circuit is operating correctly.
Seems to me the bike is running rich at/near idle and flirting with lean (deff. not rich) over 4-5k

 

I know everyone says this, but I feel pretty good about my carb clean job. They were actualy in pretty good shape when I tore into them, and they were really clean when Was done. I even broke the rack apart (so I could replace t-shaft seals). I replaced idle mixture screw o-rings as well.
I dont' seem (nor should I due to my inspections) to have any air leaks anywhere.

My hope is the answer could be as simple as "you are flowing too much air, go up on the pilot jet at least, maybe up on the main jet too OR go to stock filter and reset mixtures"

What is the big change between warm and cold that would cause the symptoms to go away once warm (but only when warmed by running over 3k rpms first...like to clear the plugs)

If I was able to work on the bike better at home I would have probably figured this out on my own by now, but I have to find time in the evenings to go back to my work where we have a shop and it's been hard to find time between other things going on right now. Couple that with we've had bad weather for the last few weeks so I only rode a week or two before the bike sat again for a couple weeks waiting out cold/rainy weather. (Alaska for you)

Thanks for the input! Keep it coming!

 

I firmly believe that your bike is like all of ours. even in nice weather, they require minimal amounts of choke to idle until completely warm. I just fired mine up for the first time since saturday, and it idled at ~550 rpm with no choke and was sluggish. I drove maybe 3 miles to get something to drink. I got home and it barely would idle at 750. I pulled in and bumped the throttle and it made a small hiccup then took off.

 

Take a ride down to see the boys at the local Auto Body Shop.
Bring an empty, clean, little jar or vial with you.
2 or 3 Dollars.
Give the guy 3-Bucks and ask for a squirt of some of this stuff into your little container:
http://www.jamestowndistributors.com/us ... rk+Remover

Get you a Dremel Tool with the Polishing Kit.
Put a few drops of the Compound on a 3X5 Card
Roll the FIRM Polishing Drum in the Compound and let it become wet with the stuff.

Polish the Diaphragm Piston Bores at Medium Speed
Keep the Drum moving.
Do the whole Bore.
Now do the other three.

That's where we start to get you Tuned-up and Dialed-in to get you out-of-the-hole.

(XJ-Bikes Special Tuning) -- Tried to resize this pic several times.

 

I'm a little confused on your post about needing choke. You say you have to have some choke to run, but that your bike was running at 550 then 750 no choke? My bike would/will idle for a short time at a very low rpm but it doesn't stay there for that long, as it slowly warms up it gains rpm until it is stable at a more normal rpm... I made mention of the low rpm more as a side note and to show that it evidently is balanced decently to run that low without dieing right away. My last XJ750 didn't want to idle lower than 950 or so without dieing. Personally I agree with you when you say the bike should need some choke till warm...it's just that my bike doesn't right now...and it isn't running quite right either...It's kind of my guess that my mixture screws being so far out, they are dumping a lot more gas than they should be obviating the need for choke. Still, it runs really good once warm and if I pull choke on at any time...well the bike doesn't like it and will die pretty quick. I'm just trying to identify where my main problem. the problem seems to be making me adjust the mixture screws much farther than normal, so i get a working situation, but it is not perfect. I want to know why I have to do what I do to make it work. From what I read, 124 should be about right for a 4-1 exhaust...so is it the filter? Does that KN make that much of a difference? Is it that the pilot jets weren't changed along with the mains? I thought I have read that changing the pilot jet didn't make that much difference. Maybe I should go back to 2.5 turns and drive it around and do some plug chops and another color tune and see what i find.
I know where to about chasing the problem, I'm just trying to minimize the chase due to my lack of free time.
Don't get me wrong, I DO DO DO appreciate the input and thoughts, etc.
On polishing the piston bores are you saying that is my problem? Or just giving special tuning advice? My bores were in pretty good shape and I did work them over a bit more...though of course not that *more*

Keep it coming!

 

the KN will make a lot of difference. in fact, a lot of guys here won't run them because of the evident changes it makes to the behavior of the bike. these things are like a precision watch and every piece makes the whole that much faster. they were designed and built from the factory to make every bit of possible power that can be squeezed from them. slight alterations to that will always create downstream issues.

as for the slide bores...
Rick is our Miyagi. I have yet to find anyone that can match his intelligence with these.
the bores build up a thin layer of residue on them which can cause performance issues. specifically, reduced acceleration and slow return to idle. by polishing them, you can greatly improve response when you crack the throttle.
I polished mine- again- last week. I used 600, 1000 and 2000 grit sandpaper with liquid wrench as the lubricant. nice and even strokes around the bore for each grit. when I was done you could see your reflection. I immediately noticed a little more spring in the step.

by the way, what color are your plugs after you take it out for a ride and get it to temp?

 

ah ha! That's what I was looking for. I hadn't read about guys not running the K&N filters...well I had read about guys staying away from pod filters, but not the KN stock style. I've felt all along that is where my problem was...at least part of it. I'll have to order a stock style paper filter and then re tune and see how it runs then. As to the slide bores, i've read all of Rick's stuff on those (well most of it I think anyway) and while the bores could always be better, mine seem to be working fine. The clunk test went perfect and I have NO problem returning to idle...quickly. Plenty of engine braking when i let off the throttle...very sensitive...so I think i'm ok on those.

After a ride, my plugs have a light tan on them, but they seem to carbon up fast at idle. Trying to help the cold issue, I think I'm running a bit too lean right now, so I'll adjust them back...the light tan area isn't huge on the plugs. I haven't done plug chops though since my first few rides, only checked the plugs after normal rides or idle runs.

Thanks!

 

Look at the Enrichment Linkage.
Make sure the Enrichment Valves are CLOSING.
You need those Valves >> SHUT ... to begin tuning.

Observe the Valves while working the Lever.
When you select >>OFF ... they ALL need to be closed without the Fingers touching the High hats of the Evrichment Valve Pull Shaft.

The "Fingers" should be Synced ... too.
Lifting the High Hats all together and BOTH Fingers contacting the underside of the High Hat.

(Chamfer the Edges of the Fingers ultra smooth with finishing paper.
High Speed spin the Rod in your drill and "Jerk-it-off" with 800 Paper putting a nice new surface on that baby)

Once the Enrichment Circuit is running right ....
Move-on to getting the Bike to:
Start with enrichment
Gradually close the Enrichment
Idle without Enrichment.
Run without ever needing enrichment.

 

Yup, checked all that both when I put the carbs back on the rack, and after it was installed on the bike AND after this problem was identified. I did clean the rod when it was apart...everything is clean and operating properly. I definitely know when the circuit is open(on) and off. It's just that right now the way the carbs are setup, it doesn't need enrichment for the most part. If I run enrichment it loads up really fast.

I think I am going to try putting a stock paper filter in it and re-colortune/sync and see it it reacts to that.
For what it's worth, when it's idling below 1k rpm, my carbtune sticks pretty much register no vacuum...I have to run the bike up to say 12/1300 rpm to get a good enough vacuum reading to sync the carbs. (if i remember correctly)

FWIW, this is the filter I have in it right now, and I don't know when it was last serviced, so it could even be flowing more air than it is supposed....I think anyway.
http://www.knfilters.com/search/product ... od=YA-1650

thanks!!!

 

Oh, 34mpg for my first full tank if that means anything to anyone. (seems a tad high, even for this bike)

 

What do you think?
Get a OEM style paper filter and see if that takes care of the issue? OR Just try servicing/cleaning my KN? $12 for the cleaning kit, but if it still flows too much then I'm no better off, vs. new oem filter for 25-40 with shipping?

 

I might have figured it out! Well, sort of.......

Yesterday I rode my bike to work and back...(not today though) so just now I went out to take a look at the plug color. (remember, this is from hot running with virtualy no idle from driving into the driveway and shutting down. Not a plug chop however) All plugs were white with a patch of light brown tan.

Then, a friend suggested I pull the filter just to make sure it isn't being TOO restricitve and at least see how it performed differently.
So, I pulled the filter, took a look at it hard to say when it was last serviced, not like there is an indicator on these.
Anyway, I pulled it out and fired up the bike.

Ran pretty much like usual. Started up and initialy idles very low, but relatively smooth. Start pulling on the choke, small rise at first but then it starts to stutter and load up. Let it idle long enough so that a twist of the throttle yeilds no hesitation and I start off. Supprisingly it didn't try to die on me like usualy, I had, however, played around with the choke some, Opening up the throttle, pulling full choke or half choke...never liked it too much. Anyway, took off and while there was some hesitation, it would pull pretty good from a standstill and would start hesitating till passing about 1.5k or soand go away by 2-2.5k. Again, tried pulling on the choke...with the throttle open a certain amount of choke would add a tad of power, but beyond half or so it would start to load up. Interestingly, it seems full choke almost works better than 3/4 which about kills it completely. Strange.
Anyway, this was a very short ride but on the second half it would hesitate and load up around 1.5-2k rpms if I would hold it there for a while. So, I rode the length of the driveway with it stuttering and not happy with me and chopped it when I got to the house. (Not too long, but not too short, say 300 feet or so.)
Took a look at all the plugs, again they were all uniform, but this time they were all thinly coated with a dark black. Thin enough that on one side of the plug you could see a brown color showing through, but otherwise coated with black...no one cylinder worse than the other

Now, one other issue I found that I had sort of suspected before and forgot about. First, I had expected that there would be some foam backing on the backof the filter so as to create a "seal" between the filter and the filter box, not letting air get around the filter....NO seal at all! And there is a small looks like cut hole in the filter box on the right forward corner...perfect place for extra air to enter and right there at the filter/filterbox seam. And second, I realized that the filterbox cover had NOT been holding the filter tight up against the box! So, it looks like my filter had been just laying at an angle in the filter box!?!?!
SHAME ON ME
While I can't say 100% that this was the case, I am pretty sure as I pulled the rubber boot out of the top of the box cover and watched the filter as I put the cover on attempting to catch the filter, and it didn't catch. I had to hold the filter in place and then possition the cover in place and it would barely hold the filter up against the box, and with no foam or sealer, it wasn't a tight fit.

So, maybe the KN does flow a lot more air than a stock filter, BUT, I think my mail problem is I have esentialy been trying to run and tune with NO filter for all I know. Maybe THAT is why I have to have my screws almost all the way open, choke not work as usual, be rich at idle but lean at power despite the upsize on the jetting.

What do you all think? Did I find the culprit?

Right now, I htink I'll find some sticki back foam, clean/service the K&N, take a look at the box cover so that it more reliably holds the filter in place and THEN go back to the drawing board with mixture adjustment.

Oh, and I once again checked the enrichment circuit for mechanical working right, and everything is at it shook. All valves close fully and are not hanging up, so unless I have a hole at the end of the needles, I am pretty sure I'm good there. All my plugs have always bee pretty uniform, so I don't see that as a smoking gun..


Thanks!

 

Yes.
You did.
When you need to add Enrichment to the Mixture to make Power ... you are running too LEAN.
Forget about using the Color of you Plugs as an indicator until you have run it -->> WITHOUT >> ANY >> CHOKE.
Just as soon as you add Enrichment to your Mixture the Plug Chop is invalidated.
Just a few seconds of Choke can darken the Plugs-up-good.

If you HAVE to ADD CHOKE ... its too LEAN.
Or
You have Air Leaks.

If you tested for Air leaks and found none ... ADD some Richness.
I don't know which Holes need the Juice because you were running with Choke on.

Run it with NO Choke.
Find-out which Holes are Lean
Give those Holes more Gas at the Pilot Mixture Screw
Add the width of a Nickel at a time until you get it looking very good then do Tweaks at the with of a Dime.