1981 CB750K - Repair/Tune-up

[cdaiscool]

I actually did wait, but figured the hose was already off and therefore wouldn't be able to get it out since it was already loose. And I couldn't twist it off with my finger. And I waited a good while (probably nearly an hour) before I tried to remove it.

I was going to go do the nut tie-down, but I'm starting to feel the effects of the last few nights. I think I'm going to call it a night on mechanics, wake up early tomorrow, do it, throw stuff in laundry (part of my moving process; where I'm moving is pay laundry, here it's free...) and then go for a quick highway run to make sure she's good on the highway.

I've never done highway before. I did 80 on the way home tonight, and my speedo's reading off a fair bit, but never done it on a highway... where I know the cop's hiding area...

I should get that cell phone holder tomorrow, and use Trapster. Hmm.

Sorry, can't do video of that. I'm NOT holding my cell phone as I ride. I wonder if I can get super-long headphones to go from my phone to my helmet so I can listen to music or Trapster warnings as I ride.

[cdaiscool]

Ugh. So tired.

Left Northville around 7 pm, got to Holland around 9:15. Got to start rounding up basic tools (chain adjustment etc) around 10 pm, got back on the road at 10:30 or so. Got gas before leaving and halfway back to Northville.

It was COLD last night. Bitter cold. Not something I want to re-experience. But at least I can say I did it...

Bike is now at my family's place, and I'm planning to hit the road tomorrow evening with it. Did quite well! I need to air up the tires though. I didn't have access to an air pump last night, and the gas stations I went to I didn't see any. I suppose I could have looked harder at Flying J, but I was too tired/cold to think at that point.

I would have gotten back around 1 am probably, but my buddy, in his infinite wisdom, decided to go 60 in a 70 mph. He was in the warm car. I asked him multiple times (every time we stopped so I could warm up, essentially) to speed up, but he refused to. Said he was getting tired and getting into 'cruise mode'. I watched as a semi-truck passed him - twice. The same one. We passed him before Flying J, then he passed my buddy, then Brett passed the truck. Then we stopped at Flying J. Then we passed the SAME truck, then the truck passed him.

I didn't get home until 2:15 am. I should have been back by midnight or 1 am, latest.

I also got lost on the way back. Saw a sign that said 'Northville - exit now'. "Wow, I thought it was further down, guess not!" and turned. My actual street I live on IS further down. So that little detour probably cost me another 10 minutes.

But, at the end of the day, the bike performed flawlessly for 200 or so miles. Going to make that trip again (there AND back) on Sunday. So it's awesome to know that it's good for it. Now I just need to check the chain before I go for another ride. It's been approximately 250 miles, so it's time.

[shinyribs]

Thats great man. I'm glad its working good for you. Did your new gear ratios work out good on the highway?

[Half-Caf]

Your friend and I must have a different definition of "Cruise Mode"

[cdaiscool]

My speedo is off, but at 75 mph I was app. 6500 rpm. So I was doing 80+ at that speed.

Not bad.

SO much better than 65 mph at that rpm. And stumbling. Now she's smooth power delivery. I'm going to put up a CL ad today if I get an opportunity looking for someone to tune the bike. It said I got 34 mpg on the way down here. Granted, the gauge is reading low so it's actually higher, but it's not off by a ton. Perhaps by 10 mph at 70, I'm going to get the cell phone holder you mentioned before this weekend, and test it when I make the trip Sunday. But I also know it's running super rich. So if I can get 'em tuned tomorrow or Saturday, that will give me a definitive, empiracal data to go against.

As for my buddy's cruising mode, we estimate (estimate!!) that he's totalled out 4 cars. It might be higher. This includes a 1-month old car. He also gets a LOT of speeding tickets. So he cruises way under the speed limit now. When I first got up on the highway, I blasted up to 75 mph. Within a minute, I couldn't see tail lights behind me. He later told me I was pulling away when he was at 75, and I was pulling pretty good. I ended up having to slow to around 55 mph so he could catch up. Not what I wanted to do...

[LukeM]

34 mpg at 80+ mph is probably about right.  Normally I was getting 40-45 with my CB, and I almost always did the limit.  I remember 65mph was about 4100-4300rpm in 5th gear. Your mileage may vary.

Been waiting for a while to use that line.
Luke M

[cdaiscool]

With my gear ratio, I expected -slightly- better than that, low 40's at least.

Honestly, if I get it tuned, and had an accurate speedo, I would say I probably am realistically getting low 40's.

It also didn't help that my tires were a little low on pressure. Low pressure = higher gas use. So I'm going to fill 'em up to the tire specs before my next ride, get it tuned hopefully this weekend, and go from there.

I also have a potentially nearly-dead cylinder in cylinder 2, so that's also most likely affecting gas mileage.

Just so we're clear, I was only going 65 - 75 really. I hit 80 initially, but I also rode from Holland, MI to Northville, MI last night. That's around 160 miles.

http://g.co/maps/h389r

That map shows also the route I took when I got off at the wrong exit. Count probably 20 minutes or more in 4 grand total stops (2 gas, 1 thought I'd lost my phone, 1 rest area to warm up) plus buddy's cruising speed, and that makes for a long, cold ride.

[cdaiscool]

Plus, my tach showed roughly 5500 rpm most of the way down. Obviously the tach might be off some, but that's what I expected. I showed 60 mph at that rpm, and my buddy said we were at about 65 mph in real life. That's expecting his speedo to be accurate.

I'll get Trapster going on my bike and then we can judge more accurately.

But for now, lunch!

[cdaiscool]

Whee!

Since I've ridden the bike to Northville from Holland, I've been riding it a fair amount. To Woodward on Friday, to Holland and back on Sunday, to work once or twice. I've put over 600 miles on it thus far, and it's been 5 days (including today, when it's supposed to rain).

So far:

-After a 9k rpm rev-out/run, after decel I heard a clanging that was happening. Scared me, and it happened over bumps but didn't feel shakey. Thought seat was perhaps coming loose, though the seat didn't have any wiggle. Rode home, since I didn't want to stop and find out that it was something that'd cause the bike not to restart, and the drivetrain wasn't having issues. Got home, found rear right turn stalk missing. Wires were just hanging. D'OH!

-Noticed after getting to Holland for a meet that the left plastic side cover went missing. Not sure where it's gone.

-Yesterday, while on the road, my turn signals just stopped working. Previously, even with the back one gone, the front one worked (I think) and the left side worked (I know). Now they don't light up.

-Tires had 30 psi when I rode back from Holland Wednesday night. I got them filled back up to normal psi, and WOW what a difference. I mean, it makes sense that they'd be bad at only 75% of air, but WOW that made a difference.

-After several hours, she starts breaking up at higher RPM again. Goes up to around 7k RPM, then it starts cutting out like it did before. I thought the tank was going dry (after only 60 miles after getting a fresh tank!) and nope. Just breaking up. I didn't take it up that high on the way back, so unsure if it was a heat-related issue, or something's changed. It was revving that high from Northville to Grand Rapids, but entering Grand Rapids it stopped and the rest of my ride (40 minutes approx) it did the same. Even with the clutch in, it wouldn't.

-Speedo is accurate to around 55, 60 mph. Then it slows down. At around 70, it starts dragging and actually being around 5 mph slow. I'm thinking there's old grease in the speedo cable. Will follow seestheday's guide this winter and clean that out.

-Still not used to how the bike tracks the road. I thought the handlebars were getting shaky at 55 on the way home. Took to my place in Holland, and got it on centerstands (first time alone!) and checked the steering. At exact center, it drifts to the left - slowly. But overall, I think it's good. No play, no wobble, no odd stuff.

-Got gas 3x this weekend, twice at the same gas station - once to Holland, once on way home. Both times on reserve. Lady recognized me, said I was getting too much gas. Too bad she wasn't cute. Girl working next to her was, though. :D

Overall, except for stuff falling off and losing blinkers, it's been a good bike! Checked the chain before my 300+ mile weekend trip, after bike had around 250 miles, and the new chain had the EXACT same slack as I gave it. 1/2" with my brother, around 50 lbs lighter than me (I think) sitting on the bike. Is that too little? Should it be more slack? I set it to 1" with the bike on the center stand when I put the chain on.

[cdaiscool]

So, yesterday a new issue popped up.

Yesterday was especially windy. Felt the bike going everywhere at 70, 75 mph. One time felt the back tire slide out from under me, due to wind. Thought I was imagining things, kept going.

Well, about 5 miles from home, in a curve on the highway, started leaning over for the curve and the rear end gave out again. Was able to stand it up and not lose it, thank goodness. But now I'm wondering what was causing the rear end to literally slide out from under me. It acted like I was in oil or something though there was none where I was.

Tire pressure checked around 4 hours later was good. Tire calls for 40, I was at 40. Not sure what else could have caused it. Tire is nearly new, but am going to check the date code on it when I get home today. Could something besides an old tire cause it to be slick? I haven't washed it, it hadn't rained, there was no water involved at all. No cleaning products.

Also, in true fashion, something else fell off on my 150 mile ride yesterday. A muffler slip-on. Now it sounds like I have a dirt bike. Scared me when I was going 75, working to keep the bike up (it kept getting pushed to one side of the highway; had to keep countering the wind, never had to do that before) and it sounded like the motor was giving up the ghost. Nope, just exhaust.

Also discovered that my horn doesn't work. So neither horn nor blinkers work off that switch. But high beam does. So I need to look at wiring diagrams to see if horn, blinkers share something that the high beam does not.

[cdaiscool]

Also, when getting gas, I found I only got 23 mpg on the last tank. There wasn't really any stop-and-go on that tank either. It was largely highway or backroad riding, probably 75% highway 25% backroads.

I got better than that in my turbo'd Integra.

[rrgunslinger]

Four Carbs and four Cyl do not necessarily equate for good gas mileage.  These bikes only make about (on a good new motor) 68 HP hauling around 500lbs (not counting body fat) :).  And when you think about it, if you don't have a fairing it's like riding a brick into the wind.   Running 75 in high winds?  I'm suprised you got 23mpg.   I had a 94 Kaw Concours back in the 90's that I was running at 72mph and got hit by a strong wind. Before I could react I went from the right lane to the left lane sideways.  Thank goodness it was a devided four lane Hwy or the our come could have been bad (I believe it was hurricane Fay).  I slowed down and the problem went away.  Just saying...  As far as you rear washing out, how is your shocks?

On Tue, May 29, 2012 at 8:09 AM, cdaiscool [via Honda CB750'S] <[hidden email]> wrote:

Also, when getting gas, I found I only got 23 mpg on the last tank. There wasn't really any stop-and-go on that tank either. It was largely highway or backroad riding, probably 75% highway 25% backroads.

I got better than that in my turbo'd Integra.

Turbos, Hondas, 4-bangers, what could go wrong?

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NAML

[cdaiscool]

As far as I know, they're good. They do need to be adjusted, they're on the lowest setting and I haven't been able to get them tightened. I've tried, but definitely isn't something I can easily to.

23 mpg is normal? The high winds was only 1/2 the ride. The other half was much better; trees, nature, no wind, etc.

So if 4 banger/4 carbs isn't good on gas, how's people getting 30+ regularly? How's my dad getting 48 on a full-dressed Goldwing? I'm not looking for that good, but there's a WORLD of difference between 48 and 23. How can my bike, with less weight, going 6k rpm on the highway cruising, get less than half of him?

I get that I have to get the carbs sync'd, but less than half? Something just doesn't add up here!

[rrgunslinger]

Maybe you rear break is dragging.  Just thinking about you slide out... a slight lockup could have caused that.  Just fishing here.

On Tue, May 29, 2012 at 9:50 AM, cdaiscool [via Honda CB750'S] <[hidden email]> wrote:

As far as I know, they're good. They do need to be adjusted, they're on the lowest setting and I haven't been able to get them tightened. I've tried, but definitely isn't something I can easily to.

23 mpg is normal? The high winds was only 1/2 the ride. The other half was much better; trees, nature, no wind, etc.

So if 4 banger/4 carbs isn't good on gas, how's people getting 30+ regularly? How's my dad getting 48 on a full-dressed Goldwing? I'm not looking for that good, but there's a WORLD of difference between 48 and 23. How can my bike, with less weight, going 6k rpm on the highway cruising, get less than half of him?

I get that I have to get the carbs sync'd, but less than half? Something just doesn't add up here!

Turbos, Hondas, 4-bangers, what could go wrong?

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NAML

[cdaiscool]

I'm going to take this to a mechanic once and for all. I'm not risking my life because I'm too proud to have a professional turn a wrench.

I'm going to try getting in today, and not riding until they've checked it over. Having a rear tire throw itself out from under me, twice, in 1 ride is enough for me to let someone else check it out.

[TOOLS1]

With one cylinder not running up to par it is reasonable that, you would loose some mileage. If the bike was running perfectly, it would be getting close to 35-40 MPG
TOOLS

[cdaiscool]

Ya, that's a good point about that cylinder. Especially between that and the carbs needing to be adjusted.

Though I don't know if I should do that until I get a new exhaust or at least this one figured out, considering that slip on fell out, and it looks like it was welded before. Shoddy welding, if it comes out on the highway while cruising.

[TOOLS1]

Happened to my buddy last Sat on his 81 GPZ 1100. Going down the road, and spit the baffle right out of his Sidewinder.
TOOLS

[shinyribs]

I rode 235 miles yesterday.No interstate,all 45 or 55 mph two lane blacktop,or curvy country roads. I would say I never dropped below 40 or 45 mph for pretty much the entire day. I refilled twice and both times got 46 mpg.   You should not be getting poor fuel mileage.You should be getting at least 35 mpg,I would think

[TOOLS1]

He's running with low compression in one cylinder, so it's understandable.
TOOLS