Topic: Mo the 80 CB650 Custom: "As the Spanner Turns..."

[754]

"I just goong  by my butt dyno and kind of reading the plugs"
 Excerpt from earlier post.
 This is part of your problem, or most of it..

 While some can feel the jetting by how it acts, many cant.

 If you are doing the following, its your main problem:

 You run the bike with a new jet combo & are checking say midrange.. instead of holding it there for a minute or two, killing engine, and getting it into neutral and coasting to a stop THEN pulling plug.. you are backing off the throttle , leaving it run into another range or two, then checking plug. That will NOT read what you are trying to find out.. and wont help..

[manjisann]

The MPG depends on your throttle use

Sooo If I don't use the throttle will I get many mpgs?? 

Insert Quote
"I just goong  by my butt dyno and kind of reading the plugs"
 Excerpt from earlier post.
 This is part of your problem, or most of it..

 While some can feel the jetting by how it acts, many cant.

 If you are doing the following, its your main problem:

 You run the bike with a new jet combo & are checking say midrange.. instead of holding it there for a minute or two, killing engine, and getting it into neutral and coasting to a stop THEN pulling plug.. you are backing off the throttle , leaving it run into another range or two, then checking plug. That will NOT read what you are trying to find out.. and wont help..

Does it really only take a minute or so to leave readable deposits on the plug?

I don't really have anywhere to do plug chops that I can get into 4th or 5th gear and really floor it. There are a few hills nearby that the speed limit is 40 mph. If I short shift her as fast as I can into 5th, I can really dog the engine and get it to WOT, will this work? The only issue is, again, it's only for a minute or two.

I realize my butt dyno is about as accurate as a blind man at a coloring contest, but in all honestly it's about all I have. With the clips high as they'll go on the 120's, there is a serious flat spot with burbling in mid throttle that doesn't get better unless I either go WOT or below 1/4 throttle and the bone white plugs, I'm inclined to believe I'm lean in that throttle range.

As I no longer have the stock carbs, and I've already spent money on this set up going back isn't really an option. My methods are imprecise, but they are all I have to work with, so I'll keep at them untl I can think of something better.

Brandon

[754]

You dont have to be in top gear to get a plug reading..

[manjisann]

You dont have to be in top gear to get a plug reading..

ohh, well that's good then. Sorry, most of the plug chop instructions I had read said you needed to make it into 5th gear.

If I do a carb sync, then install freshly cleaned plugs ( I have a pneumatic cleaner that seems to do a good job ) and ride less than a mile to get to a hill, do a WOT reaching approx 25mph would that be enough to get a good reading, or do I need to get going faster? I have 2 hills in mind to do this on, but one is around 5 or 10 miles away and the other is closer. The further away one has a 40 mph limit. I have two sets a pretty new plugs, they are both new as of the beginning of the year, and don't have more than 100 miles on them.

If I need to use the faster hill, I can take along a second set of clean plugs and change them out at the bottom of the hill before going up (and hopefully not have too many people stop and ask if I need help  .)  Sorry if I'm being ignorant, just trying to determine the best options I have using what is available to me.

Thanks all!

Brandon

[754]

Your plugs are changing all the time.. clean or not.

 Try to hold it in the range you are checking for as long as you can, then pull clutch, kill engine coast to stop, check them.

 At the drags, its a 12 second or less ride at full throttle..

 Its the changing of throttle, letting it run in a different range before you can check it, that gives flawed results..

[manjisann]

I checked the valves, they were still at .002 intake and .004 exhaust, so right where I left them! Put the carbs back on and started to do a carb sync. I was just fine tuning when..... SNAP, I busted the post that pulls the slide up  Note to self, LOOSEN the locking nut, then attempt to adjust the slide. So now I'm off to find a replacement part.... wonder how much I just cost myself 

754, thanks for the info, once I get this part fixed in my carbs I'll attempt a plug chop. If I only have to hold it in range for a few seconds to get the plugs colored then I can do that.

Anyone know where a stash of carb parts for a 74 750 carb are??

Brandon

[Soos]

Anyone know where a stash of carb parts for a 74 750 carb are??

Brandon

In my garage.



I need to get you that tank as well, are you still interested in that little wind screen?



l8r

[manjisann]

In my garage.



I need to get you that tank as well, are you still interested in that little wind screen?

Haha, well I managed to find some replacement parts on ebay, for $15 a piece I get the rod, slide and needle. I'll obviously just replace the rod, but spare parts are always a bonus to have on hand, and since I only needed 2, I'm happy. I will have to pick myself up a set of carb parts when money gets better.

I'd forgotten about the wind screen, yeah, bring it over and I'll check it out. And the tank would be totally appreciated, I have a couple ideas I want to try out on a mostly buggered tank before I start tearing into the relatively sound one I have. Let me know which day works best for you 

On a slightly different front, a co worker picked up my bosses 1980 cb750 DOHC and I've been helping him get it running right (and I haven't really even broken anything on it.... yet    ). It has been really interesting and educational to help him and get to see the bike up close. I swear the frame is the same as Soos's 79 650 down to the side covers, the only mods I can see that were done presumabley to fit the CV carbs and DOHC was to chop the spine about 8 inches before it met the back and weld in a few bits, and then run two braces from the back forward to the down tubes. What I'm getting at is a lot of the non engine bits are probably a direct swap, things like controls (NOT control cables, just the electrical) MC, forks, calipers, things like that. Just a tidbit of info.

His carbs were leaking fuel and we've been fighting that. I think we finally narrowed it down to the float needle springs were a little warn so it was allowing the fuel to fill too much. The floats are plastic and unajusteable, so the only way to fix float height issues is with new needles. Since the bike is his only means of transport, and seeing as how mines currently not running (curse my Herculean strenght  ) I canablized my needles to get him back on the road until the replacement needles get in. That seems to have fixed the leaks for the most part.

It was nice working on a bike that wasn't mine, and his carbs aren't too bad to get off and on in stock configuration.

Brandon

[Soos]

Yeah I bet his DOHC 750 looks like mine suspiciously....


My front end dual brake setup is off one.

I actually used my '79 cb650 rims, the dohc lower legs, brake disks and bolts, and the calipers.



Good bikes when running.
Mine was DOA, and got dismembered in short order.


And yeah that tank o mine is buggered. Looks something like Niagra falls when you pour gas in it.
Glad someone can use it.




l8r

[manjisann]

While my little brother worked on cutting out parts for my trucks bumper, I put in the new parts for the carbs and stuck them on the bike. I synced them pretty close, they aren't exact, but very very close. I figured out something rather important. My idle circuit is running super lean, even with the air screws in almost all the way, I believe they are only a quarter turn from seated. Guess I'll be using those new pilot jets I bought after all. I'm going to try putting in the new idle jets tomorrow and see if I can get the idle circuit to behave a little better.

I also noticed white smoke coming from the cam breather filter and thought it was smoke indicating that the oil was getting too hot. I did a search for this and found a thread where someone stated the white stuff was actually water vapor from the hot oil. As I understood it, the humidity from the air mixes with the oil and then gets turned into vapor or something like that. They also suggested ignoring it. I think I'll be running a longer breather hose then.

Thanks,

Brandon

[Soos]

Ahhh.... I forgot those carb parts too!

Look for those too!



l8r

[manjisann]

Soos, don't worry about the carb parts, I got spares off ebay 

I did some plug chops today and had some interesting results. I believe the 120 is too big, when I loaded the bike down in first gear by pressing on the foot brake and went WOT, she bogged really bad. When I tried it in second she died. I pulled the plugs and they were black, so I'm pretty sure she's WAYY to rich on the main. I plug chopped mid range throttle and found it to be just slightly rich.

I went to put the slow jets in annnnnd... THEY'RE THE WRONG SIZE!!!! so they don't fit!! DAMMMIT!!! The bummer part is they are not returnable.

I checked on JetsRus and apparently the correct sized ones are no longer made. They have some that are slightly longer and the sight says to just dremel them down.

Once the weather stops raining I think I'll just run it like this until I can get the right jets.

Thanks,

Brandon

[manjisann]

Rode to my sisters house last night to see her and my niece again, no problems with the bike and only one homocidal tin top that tried to run me off the road    oh well, gotta take the good with the bad. It was sprinkling a little (been raining here... Utah is supposed to be a desert, what gives??) Made it to her house and back with no real problems, parked the bike, gave it a quick once over and went inside.

Fastforward 6 hrs, I get up, it's still drizzling a wee bit and I've decided to ride in to work. The power was out at my house, so I was using my mini flashlight to gear up. Geared up and left, after about a mile looked at the speedometer.... and it was reading 0mph.... I just replaced it!!!!! At the next red light I leaned forward to check if I could see what was wrong and the speedometer cable had come loose...? So while it was sitting idle in my garage the cable came loose... Gremlins anyone? 

I pulled over and threaded it back on and took off. After a minute I noticed an annoying whirring noise that didn't go away till I dropped below 10mph. I'm pretty sure it's the Speedo cable making the noise, guess I'll lube it, athough I swear I did a month ago. All in all a wierd morning.

Brandon

[Zaipai]

... Gremlins anyone? 

Oh yea, they visit this house all the time.  Its nice I can blame them for all sorts of things..

Glad its running good and things are for the most part worked out.. homocidal tin top? I hate those..

.: Scott :.

[manjisann]

homocidal tin top? I hate those..

There's a fair number of them here in Utah. I've mostly had good experiences, but guess this person didn't get the memo, oh well.

I rode home in the pouring rain yesterday, that was a different experience, but not too terrible. When I got home I quickly changed and went out to the shop and dried the bike off pretty good. I changed out the clutch cable to a new one. When I adjust it the way the book says to if I have the bike on the centerstand and it's in first gear the rear wheel spins with the clutch lever in, so I know the clutch is still partially engaged. Has anyone else noticed this and is it normal? If I adjust it so the rear wheel won't spin when the lever is pulled it won't engaged until it's almost all the way out. I'm probably overthinking this.

I regreased the speedometer gear with white lithium grease, and it seems to have fixed the mystery whirring noise.

I think I fixed the auto kickstand issue. It seems that somehow the kickstand I'm using came from a cb500 or 550 and is slightly shorter than the 650 stand. I tried putting a 650 stand on but things just didn't line up and it was even worse than the current one so I went back. I finally had the brilliant idea of trying the spring off the 500 frame and that seems to have done the trick. I also had to cut the bumper bracket off the mufflers that the kickstand was supposed to rest against, this allowed the stand to come up just a wee bit more and I'm hoping with all this I won't have any more problems. I think when I get around to redoing this bike in a few years I'm going to try and find a different frame so I don't have the jacked up kickstand issue. But for now she seems to be rideable again and that is all I care about.

I'm still waiting on the slow jets and I'm hoping that will fix part of the surging issue when I'm riding. At low throttle it's not smooth, once I open past about 1/4 it seems to pick up power and smooth out, and WOT pretty much kills it    So still planning on the bigger slows and will likely try stepping down to a 115 main. Hopefully this will also improve the piss poor gas mileage I'm getting. Filled up yesterday, 73 miles on the clock, 3.1gals of fuel... err. I know I had some leaks and was messing around testing stuff, and I'm pretty dang sure I'm still too rich at WOT and rich at 1/4 to 3/4, so once all that is ironed out I'm praying for at least 40 mpg. I've put so much money into getting these carbs to work that I'd hate to have it bite me in the posterier in the mpg dept. I'm just musing, not obsessing, so don't worry guys, I'm still happy 

Brandon

[manjisann]

JetsRus.com is a really great site, ordered on Friday evening, he shipped on Saturday complete with tracking, I received today! I realize that some of the credit goes to USPS, but you get the idea, AND they are the right diameters. I'll install them tomorrow. Other than finally figuring out why my breaks were dragging so much (I have REALLY got to stop leaving parts off that the brilliant and well educated Honda engineers deemed necissary), it turns out the rubber band on the caliper bolt is VERY necissary for the proper function of the thing. I can now get the front wheel to spin 2.5 times at least, whereas before I was hard pressed to get 1.5. I am tempted to do a test to see how much my mpg improves just by doing this, but I'm impatient and want to get the slow jets installed and tuned to see if it gets rid of the minor surging and popping at low throttle. 

I've decided I'm one of the luckiest members on the forum because I live so near Soos (admit it all of you, you are jealous  )  I came home the other day and looked in the mailbox and to my surprise there is a huge bag full of 750 carb parts, almost enough to make another set! Guess Soos was tired of looking at them and decided they'd look better in my garage, and you know what, he's right     This pretty much seals it, I'm gonna have to come up with another set of bottletop 750 carbs for the cafe. With as much tinkering as I've had to do trying to get them to work with my stock 650 I should have most of the parts and knowledge to get them to work on a hopped up 650 Soos piston special engine    Sometimes I just sit here and think how different things would be without the awesome members of this forum.... eh it'd suck, everyone here is just too cool  Well everyone have a good evening!

Brandon

[Hush]

I'm sending you some good ole Kiwi Gremlins as yours seem a bit whimpy, undoing the speedo cable indeed!
Gremlins here throw your #3 piston though the case at 150 kmph.

[manjisann]

I don't think Customs will allow imported Kiwi Gremlins, they have no natural enemies 

Brandon

[manjisann]

I put the new 42 slow jets in and started with the air screws at 1 turn out. I ended up at 1/4 turn out and the plug still looks lean, but theres some greying on it, so I'm getting there. I'm going to step up to a 44 when I get some cash. Mid range and WOT are still pretty rich.

The front brake still squeaks ever so lightly, it's mostly un-noticable. I'm going to order a new rubber bolt thingy and see if that helps. I saw a diagram that showed two of the bolts with rubber thingies so I may try that and see if it causes the brakes to retract enough to let the tire spin freely. Something to consider for later.

Brandon

[manjisann]

New rubber brake bolt bushings ordered from Bike Bandit at $3 a piece, not too terrible.

I decided to buy some 115 mains yesterday and put them in. I couldn't ride because of some family commitments and the weather was pretty crummy. I took the bike for a ride going through just about all the throttle positions and came back home and pulled the plugs. 2&3 were a little lighter than I wanted but not bone white, 1&4 were really sooty and black. After giving it some thought I decided to put the 107.5 mains back in 1&4 and leave the 115's in 2&3 (seems I'd read somewhere about sometimes having to jet differently between carbs when running pods, so figured I'd try it.)  I left the plugs dirty and just rode off. I went for an 80 mile ride like this and about half way I did a plug chop at half throttle (about that, I was going about 55mph at the time and didn't feel like staring at the throttle grip I'd taped to see exactly where I was.) I pulled over and pulled the plugs, all 4 of them looked pretty similar, a little lighter than I would like, but not too bad. At WOT the bike runs pretty ok, nothing like the bogging I was experiencing earlier, so without a plug chop to confirm I'm going to go out on a limb and say that the mains are just about where they should be. I'll have to try a plug chop a little later, but for now I'm relatively happy with where the mains are at. I just need to lift the needles a wee bit to enrich it, and up the slow jets. When I filled up I found I was at a little over 39 mpg!!!! SOOOOO much better than the approx 23 mpg I was getting. I think fixing the front brake and the jetting must have helped. I'm hoping to be able to eeek a few more mpg, but for now I'm super pleased. Here's a couple pics, please forgive the crappy quality of the pics, I only had my really old camera phone with me.

Brandon

[scunny]

good to see you're getting it sorted. looks like a good day for sheep 

[manjisann]

I saw the sheep and thought of Hush    It was pretty funny, a car passed by and it didn't bother them, but as soon as I started back up and accelerated out there, it was a fuzzy air filter stampede 

Yeah, it feels like I'm closer than I have been. It seems as though it's still running lean, but I think I'm on the ok side of lean. I'm going to run like this for a wee bit while I try and recover from all the spending I've had to do getting up to this point. I'll see what happens when I lift the needles, hopefully she'll get some color on the plugs, right now they are a lightish grey, I'd really prefer a light tan. I also need to take a magnifying glass and see if there's any of the little glass balls forming on the insulator. Considering I made it back from an 80 mile ride where I flogged her pretty decent (got up to 70mph while trying to do a WOT in 4th or 5th can't remember, that is now the fastest I've ever been on a motorcycle  ) and she still starts like a champ I'm thinking I'm ok for a short bit. I've really thought about it and I think I'm going to step from the 42 slows to 48's. I've been reading TT's post on plug chopping and it's my understanding that the Idle circuit should be a wee bit rich, and since 42's are pretty white even with the air screws only 1/4 turn out, I'm thinking 6 steps up is a good shot. I just hope that won't kill my mpg too much. I'm also going to try and stay around 4-4500 rpms in the city, that should help with fuel savings.

I'm pretty stoked, there was many times I wasn't sure I'd get to this point, sure is nice to be here! Thanks to all you awesome forum members, dare I say friends? I really couldn't have done it without you!

Brandon

[scunny]

to test your lean theory, try the choke in little increments, saves pulling the carbs all the time.

[Hush]

About time you sorted that bucket of bolts out Brandon, we thought you were going tp make it your lifes' work for a while there.

[754]

Bradon, them grey-haired gals in the pic figured your bike was runninng.. not baaaaaaad  !!..