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Discussion Starter · #1 ·
ok so I just got this thing up and running, and it seems like 1 step forward 2 back...
First I'll say that I just got this bike in minimal running order. Stripped the carbs cleaned and blew them out with air.

I have:
carbs-
cleaned
adjusted
adjusted idle/mix
checked seals

ignition-
adjusted gap in the point and cleaned
adjusted timing
new plugs, adjusted gap (though they might be fouled by now?)

changed the oil
checked the compression
new battery
adjusted valves


The only thing I haven't been able to do is sync the carbs, or properly adjust them all the way.
when i pull the plugs the color looks ok, BUT, it doesn't run right. It use to idle ok, but now it idles ok for a couple of min. then just shuts off, if I crank the RPM up it seems to be ok. But the revs never seems to sit still unless it's above 3K, it's minor but you can hear it. Next it doesn't seem to rev that fast, though like the power I have nothing to compare it to.As for on the road, it seems to go fine, starts fine even when cold. The power dies a little on the top end but it still goes. Then after about 10 min of running it seems to over heat, I lose power, it start to miss fire and if I let out the throttle it'll die and not start for about another 10.




Not really sure where to go from here. I'm going to replace the plugs and the point (would have done this but was sold the wrong ones) but somehow I don't think that's what is wrong.
 

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Sensei
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The FIRST thing you need to do is check compression........... Then the Battery....Then the ignition (points, coil, and plugs)....
 

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Discussion Starter · #3 ·
Are you telling me this because it's SOP, or because you heard what I put. If you read what I put, then please elaborate on the need to check all of that again? Though I do realize that some of that could be out of wack now.


Everything that has been adjusted has been adjusted pretty much at the same time, and most of it has been checked more than once


P.S. I forgot to mention that the compression check was within speck, barely, but it was there. and was within 5 PSI of each other. BUT the right cylinder took 3-5 more cranks to achieve this.
 

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Discussion Starter · #4 ·
I might also mention that the battery is brand new, not to mention I trickle charge it almost every time I am going to start it to make sure I don't drain it.


all the electrical cables seem to be ok, I'm going to un-do all the grounds and sand the connections down to make sure the grounds are good
 

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Just because a battery is new doesn't mean it's any good. With the marginal charging systems these bikes have it only takes once running the battery down to ruin them sometimes.. Or for them to sit for just a little bit too long with no activity.. As well as the fact that you CAN buy a battery that's no good from the beginning.. They're manufactured very cheaply.

What were your compression numbers??


GB :mrgreen:
 

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Discussion Starter · #6 ·
ummm I want to say 130, or 140, but honestly I don't remember. in the next couple of days I'll have newer numbers.


the battery seems to hold a charge ok, and I haven't tested the Alt in anyway. even if the battery sits for a couple of weeks it'll start.
 

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Sensei
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Sorry Joey...I missed that you had run a compression check..... I trust that both cylinders were 160 PSI or better?
The battery is another story.....
When it was initially placed in service, did it get charged at only 10% of its Ampere rating for 10 hours, or was it just filled with electrolyte and connected?
Has anything other than Distilled water been added when it's low?

When you replaced the plugs and regapped, did you retime as well? (changing the point gap alters the timing)
Does the advance unit work properly?... (did you check with a strobe?)

Truthfully, the intermittant firing/ won't idle sometimes/ doesn't rev smooth until over 3000 sounds like a carb/fuel supply problem... have you verified good and constant flow from the tank/petcock to the carbs?... Gas cap vents?
Are floats set at 21mm?
Have you checked for air leaks at the manifold joints?

Just asking all this to eliminate possibilities........

EDIT: Just saw your post....130/140 is way below minimum spec for re-ringing/rebuild... Normal spec is 170... I tear them down at 155....
 

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Discussion Starter · #8 ·
ok, ya I spotted the compression specs in the manual to verify, it says the same as you.



I guess "being in range" I thought was 140 + but to be honest, I trusted teh interwebs for that information off some random site.


And obviously I don't want that to be the case because I bought this bike from a shop that is very trusted.
 

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Sensei
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It WILL run at 140 PSI, probably even at 120, but it won't have enough "pulling" power to get to top speeds or accelerate quickly...... I have seen these bikes limp 40 to 50 miles running on only one cylinder.......Not fast, but they got their riders home....
The top end rebuild is pretty easy and simple, but the engine has to come out of the frame.....And there's the time, services (boring if needed) and parts prices.....

"And obviously I don't want that to be the case because I bought this bike from a shop that is very trusted."...
I don't understand this statement...... If the failure/problem was caused by something you did or didn't do, YOU are stuck..... But if it is their fault, they should make it right, (that's how they got to be "very trusted")......
...Or did you purchase it "as-is"/no warranty?
 

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Discussion Starter · #10 ·
I got it as is. So If I'm stuck with it, oh well. I will talk to them, because it was a little upsetting. before I even bought the bike I was looking at it and they told me that the only thing it needed was the carbs gone through because it had been sitting. I asked them if they were sure the engine was in good condition etc and they also had said that the bike had plates and tags. and when i picked it up, it had the wrong carb on it, wrong carb kit. The DMV doesn't even have record of the bike.



Side note, I purchased the bike about a month ago and one of the first things I did was check the plugs and the compression and charge the battery before I did anything other than put fuel in it.
 

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If it hadn't been tagged for road use lately then it's probably a good sign that the battery is old, and may not hold a charge.. It sure doesn't sound like a very reputable shop to me.. I'd definitely give them a small piece of my mind about the engine having low compression numbers. See where it gets you with them...

My two cents..

GB :mrgreen:
 

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Sensei
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What do you mean, "No DMV record"?... Did you get a title?
 

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Discussion Starter · #14 ·
In California if you don't register a bike for a number of years they drop it out of the system and you have to put it back in the system (give them money) and get a brake and light inspection.


for the link: :eek: AWESOME, question though, how different is the 71 to 74 model?
 

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Joeyd said:
In California if you don't register a bike for a number of years they drop it out of the system and you have to put it back in the system (give them money) and get a brake and light inspection.


for the link: :eek: AWESOME, question though, how different is the 71 to 74 model?
The manual is just dated 1974 - also covered are the earlier (non-sloper) models.
 

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Checking compression before you run the motor doesn't give you a valid reading. The motor has to be warm, both plugs out, and the throttle has to be held open during the test. By your description, the problem sounds like ignition timing and fuel supply. Mechanical problems tend always to be the same, not to work sometimes and not other times. I'll except from that a loose connection between the carb and the intake passage - that can produce a variety of problems, like dying at a certain speed or shutting off when you come to a stop. Air filters clean? Try running without them to eliminate them as a problem. What's your evidence that the motor's overheating? That's a bit uncommon. Just on an off-chance, have you checked the valve clearance? Might be worth going over everything again to be sure of settings. I know on the 450 it can have a considerable effect on how the motor runs, and there is a change in clearance from cold motor to hot motor.
 

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tbpmusic said:
The manual is just dated 1974 - also covered are the earlier (non-sloper) models.
I'm always puzzled by this manual, why is it dated 1974 but only shows up to K4 model in preface and the last 175 (K7) was 1973, the CB200 came out in 1974. :?
 

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malcolmgb said:
tbpmusic said:
The manual is just dated 1974 - also covered are the earlier (non-sloper) models.
I'm always puzzled by this manual, why is it dated 1974 but only shows up to K4 model in preface and the last 175 (K7) was 1973, the CB200 came out in 1974. :?
Not really an issue - the only changes to K 5-7 were cosmetic.
 

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Discussion Starter · #19 ·
*sigh* well I haven't had a chance to test the compression yet. Mostly because I'm waiting to replace the point and plugs. Well that and work has me keeping me from, well anything.


I found the compression numbers I ran the first time, and it was 154PSI on both. But i'm pretty sure I tested it cold.


And I have no real reason to believe that the engine was over heating. but at the time it seemed to make sense, I thought if the timing was advanced or just running too lean after running for a while it would.... get hot.


When I get the point and plugs, I'm going to readjust everything again and go from there.


I have to say though, the only part that always seems to be a "shot in the dark" is where to set the carbs at, the idle makes sense, but that's assuming the A/F is correct. Anybody have pointers? I'm afraid this is a wild goose chase if I don't get that narrowed down
 

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Standard mixture screw setting for most 175's is.... 7/8 plus or minus 1/8 (out from gently bottomed)
 
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