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Discussion Starter · #1 ·
ok.. i have a 72 Cb175.. it was running, sort of, last week. when i could get it running, it idled at 3k, spec is 1.2k if what i read was correct.
when you go to give it gas, it would only go to 5k and it would bog down, often stalling when you release the throttle. took it out in front of my house and when in gear it had no power, it was almost like i was just riding at idle speed no matter how i twisted the throttle.
ive cleaned the carbs about 5 times now, they're both nice and clean, tho the main jet needles like to wiggle themselves loose and fall into the bowl, i usually notice it has happened when i see that side spraying gas droplets instead of exhaust, out the muffler.
ive checked the throttle cable, and it does like to stick but for the most part it moves freely, and retracts the cable nicely when i release it.
new plugs, but havent had a chance to use them yet.
i figured the reason it wasnt revving was a compression issue, i dont have a tester, but i assumed on a bike this old, and given the condition i got it, that the gaskets were probably shot.
tore apart the top end, and surprisingly, the gaskets up top were great, looked like they had already been replaced.
found 3 nuts just sitting in the bottom of the motor, no idea where they came from. but they didnt look chewed up, so hopefully they didnt damage anything.
along with the nuts, i found 2 of the 4 screw looking things that attach to the valves (i think), they were also just sitting there, i put them back on where i saw a 3rd identical screw located, but the 4th, is bye bye.
moved on to the lower end, and as i thought, these gaskets were comepletely shot.
got some gasket paper and goop, and re-did both sides, and the little gasket for the cover of the stator (i think), it was on the left lower side of the motor.
almost had it comepletely re-assembled when i remembered that the motor had rotated a bit, and the camshaft/ sprocket had also rotated, so i tore the top back apart to reset the timing. found a pdf of the manual(which is also linked on this site as well), and saw i had to set the notch on the stator, to a notch or line next it in the housing. (ill take some pics later and upload em, but im hoping you guys can translate my noob-speak lol).
now, the stator itself has 2 sets of lines. one set has "FT" right under them, the other has nothing.
i first set the 2 lines with "FT" to the notch in the housing, the pistons themselves appeared to be at the top of their rotation. and according the manual, i had to set the cam sprocket so the little "O" was at the top as well. slapped it all back together, hand cranked the motor to make sure everything moved nicely, then bolted the head and covers on. went to hand crank again, and it would not move, at all. tried the starter, just to see if that would do it, it didnt.
so i took the cylinder cover off, and it started moving again. not sure what that was all about, but it moves freely now when bolted.
i checked the valves, they were jiggling and very loose, and if i was correct in the screw i was supposed to tighten them with (the loose screws that i had found in the motor), and i hand tightend them til i couldnt wiggle em anymore, then backed em off a hair so i could just barely move em with my hand. (no gapper to check with, so im guesing here)
cranked the motor to test, and it all moved nicely. so i put the plugs in, couple drops of gas in the carb and tried starting it, and it ran. it idled high like before, but it sounded alot smoother than before, so i shut it off, re-attached the gas tank, filled it about a quarter full, set the carbs to stock (fuel out 3 full turns from fully closed, and air 1 and a quarter out from full closed), went to start it and as soon as the plugs fired, it clanked horribly loud and stopped the starter. i hit the button again, and it turned over great, but as soon as it sparks it clanks and stops.
loosened the plugs, thinking they were hitting and that wasnt it. turned it over with the boots to the plugs disconnected, and it turned over great, no clank, no nothing. reconnected, and instant clank.
i cant kickstart it at the moment, because the spindle that the kick lever bolts to, is stripped. i can use vice grips to very slowly, and carefully hand crank it, but starting is out of question.
according to what i have read, it may possibly be a timing issue, essentially, the spark it firing at the wrong time, (the upstroke of the piston), and pretty much stopping it dead in its tracks. also, it may be firing on the wrong rotation of the cycle (exhaust/ intake).

i dont know what im doing here, im just blindly trying stuff, and researching the web to find answers, but ive done all i can without some help from some1 who actually understands this stuff.

thank you so much for the help, and im totally sorry about this massive post :(
 

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Sensei
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First, you set the cam timing at the "T" line ...... The points should fire at the "F"....

You NEED to set the valves at the top ("T") mark of the compression stroke for that cylinder, then rotate the crank 360 and line up the "T" again for the other cylinder.....
You WILL NEED feeler gauges, guessing is no good.... And, those nuts are jam nuts to lock the adjustmernt (screws) in place ....

UNFORTUNATELY, I believe the "Clanking" was a piston striking a valve... (so you probably have a bent valve)......

IF you don't mind some phone time expense, I'd be happy to guide you through the steps, but I'll get finger cramps trying to explain each step on the board here...
You may call me after 8PM (EDT) almost any night at 540-427 4256, but I screen calls so start talking after the answering machine picks up.....IF I'm available, I'll answer....... ;) Steve
 

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Discussion Starter · #3 ·
how do i set the cam timing at the "T" line? do you mean matching the "O" on the sprocket, to the "T" in "FT"?
and how do i set the points to fire at the "F"? i didnt see any way to move that around when i had the cover off.
and how do i tell if its the compression stroke?

id love to get a walkthrough, but unfortunately i dont have a phone :( cant afford one at the moment
 

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Sensei
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Ok then... One step at a time it is!....

Yes, The "O" should be on the vertical centerline of the cylinders when the "T" mark is aligned with the index line (center of the "pointer")
Compression stroke is right AFTER the intake valve for that cylinder closes (The next time the "T" aligns)

You set the points by rotating the entire plate they are on..... Two Phillips screws hold it to the cam journal block (camshaft bearing)... Hold crank at F on rotor to index....Rotate points plate until points JUST break (open).....
 

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Discussion Starter · #7 ·
im sorry.. the headers are the curved pipes that exit the cylinder head and meet the mufflers, correct? also, if you cant see if theyre open/closed.. would closed be right past the wider part of the cam?
 

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Sensei
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If you have the inspection/adjustment ports open (round covers with hex) you can watch the valve and rocker (tappet)... When the valve is "up" and there is no pressure on it from the rocker, (rocker "loose" and spring not compressed) it is closed... The first valve you will be looking at is the rear side of the engine, nearest the carbs on the left (as when you are sitting on the bike) side of the engine....Rotate crank while watching this valve...The rocker will "push" it down into the cylinder, and then , as you continue turning the crank, it will allow the valve to come back up...The first "T" alignment on the index after that is TDC on the compression stroke for that cylinder......Hold the crank so the "T line" stays on the index line and adjust both left cylinder valves to specs using a "feeler gauge", locking down the adjusters with their "jam" nuts when correct.... An extra set of hands to hold it aligned on the "T" and index is helpful here....
 

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Discussion Starter · #9 ·
ok, thank you, im gonna try that tomorrow probably.. too late at the moment.. ill let ya know when its done, and ill post pix of it so hopefully you can see if i did it right lol
 

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Discussion Starter · #10 ·
ok, i have the motor apart right now. now that i can see it, alot more of what you said makes sense now lol. one problem, the backplate for the master-link on the cam chain fell in. i took the heads off, but i cant find it.. i did however find the missing valve screw, go figure.. where can i pick up a new backplate for the link?
 

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Sensei
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Probably in your oil sump..... New are available from the Honda dealers, but you have to get the part you "lost" out before it does any damage anyway.....
 

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Sensei
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The oil "sump" is essentially the bottom half of the main cases. (where the oil was).... If the plate fell down the passage (where the camchain runs) it would/could fall all the way down to the crankshaft's camchain sprocket area, and end up in the sump....I'm not saying 100% tht it did fall there, but if it's not up top, it fell to somewhere...And that's just the usual and most obvious path for it to fall....

Investing $35 in a pre-paid "disposable' cellphone might be a good idea at this point.
 

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Sensei
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It may be possible to "fish" it out (or use a magnet) IF you can locate it.....Otherwise, we'll go through the steps to get it out in stages.......
 

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Sensei
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It MAY also be possible to "wash" it into the right sidecase cover as a last-ditch effort..... But don't do this until you have eliminated the 'fishing' possibility, it almost guarantees you'll have to split the maincases.... Hopefully, the plate is sitting in some oil residue on the splash pan right under the crankshaft.......
Since that cover would have to come off to access the lower maincase anyway, it might be worth a try... IF the "fishing" doesn't work, replace the oil drain plug and add a couple qts of diesel, shaking it gently and rolling the engine over on to the right side... Worst that could happen is you'll clean some of the inevitable oil sludge out of the sump......
 
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