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fired up ct1 175 -- went rather poorly


Chunkstyle
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hi guys --

i fired up that ct1 that i've been posting here about recently, and things didn't go that well. it popped and ran for

about 5 seconds & then died. here are the issues it's having now -- i'd be grateful for any advice:

1. when we put gas in the tank & opened the petcock, gas flowed slowly thru the inline fuel filter (new) and to the top of the carb. after a bit, gas started coming out the fuel bowl overflow hose & then also out the fuel bowl vent hose. i assume this indicates the float valve's not closing (??). when i rebuilt the carb a few weeks ago (using an old keyster rebuild kit from ebay that had some different parts than were on my original carb), i thought it was odd that the float valve in the top of the bowl seemed to have just metal-to-metal contact in its closing function. there was no seal or gasket or anything -- just the bare metal tip of the needle mating with the metal seat. is this normal?

seems a poor way to positively seal against liquid flow.

2. when i got the bike, the seller said the kickstarter gear was messed up, but it could be push-started. upon first opening the clutch side cover late last spring, i found that the needle bearing that supported the kickstart idler gear had blown up & that the idler gear, still on its little stub shaft, had rattled around in there & chewed up a bit of the inside of the case, although not too terribly. i was able to find a replacement needle bearing & it fit well into its bore (the bore hadn't gotten chewed up), but the idler gear on its stub shaft, while fitting well laterally, was able to slide in & out a bit -- there's nothing i could see to keep the gear on its shaft bottomed out in the bearing's bore.

thought it was pretty much fixed, though, with the new bearing & no lateral slop.

today, after 2 or 3 kicks, the mechanism in there seems to have given way again. is this a problematic thing on these ct1's? seems really unreliable, and i've found nothing in any of the exploded views or diagrams i've seen that show how to prevent that idler gear shaft from sliding in & out a bit (which i'd bet is causing the problem now). it can move in & out about 1/4" before stopping against the back of the primary driven gear on the clutch basket.

3. how do the gears work on this bike? a friend said down is 1st, then up for 2nd, another up for 3rd, and down for neutral. doesn't seem to actually work that way though. ?? can the gears be shifted with the bike sitting still & not running?

thanks!

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Your float height needs to be set, that will stop the fuel flow. There is a little tang that makes contact with the valve; bend it slightly (to spec...helps to have a clymer) and that should fix your problem. If not, maybe you have the valve in backward?

The gears on that bike should be 1 down, 4 up. To go into neutral, shift down to first, and go up a half click. Try it first without running to get a feel for it.

Unfortunately, I can't really help with anything else. Ask these guys when they open up registration again...they should know:

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hi guys --

i fired up that ct1 that i've been posting here about recently, and things didn't go that well. it popped and ran for

about 5 seconds & then died. here are the issues it's having now -- i'd be grateful for any advice:

1. when we put gas in the tank & opened the petcock, gas flowed slowly thru the inline fuel filter (new) and to the top of the carb. after a bit, gas started coming out the fuel bowl overflow hose & then also out the fuel bowl vent hose. i assume this indicates the float valve's not closing (??). when i rebuilt the carb a few weeks ago (using an old keyster rebuild kit from ebay that had some different parts than were on my original carb), i thought it was odd that the float valve in the top of the bowl seemed to have just metal-to-metal contact in its closing function. there was no seal or gasket or anything -- just the bare metal tip of the needle mating with the metal seat. is this normal?

seems a poor way to positively seal against liquid flow.

2. when i got the bike, the seller said the kickstarter gear was messed up, but it could be push-started. upon first opening the clutch side cover late last spring, i found that the needle bearing that supported the kickstart idler gear had blown up & that the idler gear, still on its little stub shaft, had rattled around in there & chewed up a bit of the inside of the case, although not too terribly. i was able to find a replacement needle bearing & it fit well into its bore (the bore hadn't gotten chewed up), but the idler gear on its stub shaft, while fitting well laterally, was able to slide in & out a bit -- there's nothing i could see to keep the gear on its shaft bottomed out in the bearing's bore.

thought it was pretty much fixed, though, with the new bearing & no lateral slop.

today, after 2 or 3 kicks, the mechanism in there seems to have given way again. is this a problematic thing on these ct1's? seems really unreliable, and i've found nothing in any of the exploded views or diagrams i've seen that show how to prevent that idler gear shaft from sliding in & out a bit (which i'd bet is causing the problem now). it can move in & out about 1/4" before stopping against the back of the primary driven gear on the clutch basket.

3. how do the gears work on this bike? a friend said down is 1st, then up for 2nd, another up for 3rd, and down for neutral. doesn't seem to actually work that way though. ?? can the gears be shifted with the bike sitting still & not running?

thanks!

Now i dont want to overly concern you BUT.

You say the gears dont work right and the kickstart idler is floating around. Unless there is something odd going on the kickstart idler should be running on the end of the layshaft, not a stub. Any chance of a pic or 2.

Have a look here at csml, http://www.cmsnl.com/yamaha-ct1c-1971_model8381/partslist/A-11.html I assume the idler you are on about is item 24.

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thanks for the replies!

turrican64 --

i did set the float to the height spec'd by my clymer book (with the carb upside down, i believe it was 1" from the rim of the bottom of the carb to the top of the float, without the float needle's spring being compressed).

gear-wise -- can you please explain what you mean by 1 down 4 up (i'm a complete motorcycle novice)? are there 4 or 5 forward gears on this bike? i can't figure out how to tell what gear it's in -- i'm guessing you have to get it in neutral, where the bike rolls easily and then shift up from there. aside from neutral, i just can't tell which gear it's in at any given time. i understand about using the top of your foot to lift the shift pedal for some of the gears, but it's quite confusing for an utter newbie to figure out where you're at, gear-wise.

cynic --

i didn't mean that the gears are definitely not working (could be, but i'm not sure) -- it's more that, as a complete novice, i can't easily tell what gear it's in (i assume it needs to be in 1st to push-start it, since the kickstarter died), and the shift pattern's hard to figure out when you can't tell what gear it's in at any given moment. after the kickstarter died, i spent some time trying to push-start it, and i'd imagine you definitely need it to be in 1st gear for that to work, and i simply couldn't tell what gear it was in nor how the shifting worked.

regarding the kickstarter idler, i checked out that exploded view you linked to (thank you), and the part i'm talking about isn't in that view. it looked like that view was of the trans parts -- this kickstart idler is in the right side of the case, just to the right (as you're facing the bike's right side) of the main kickstart shaft (that the kickstart lever goes on), partially behind the clutch basket. it's a metal gear circlipped onto a short (maybe 1 1/4" long) shaft that slips into a needle bearing in a blind-bottomed hole machined in the right half of the engine case, facing toward the clutch basket. it apparently is for transferring the rotation of the kickstarter's main shaft (when kicked) to the primary driven gear on the back of the clutch basket. picture-wise, the case is closed up now, but i'll scrounge around & see if i have any old pics or can find any diagrams. it's really weird, though, how that stub shaft and the gear are free to slide in & out of the bearing a fair amount without any apparent method of keeping it more fixed in place.

thanks again for the replies -- i'd appreciate any further input.

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Is the part Here?

I would always jump start a bike in second gear. Find neutral and then click the gear lever up once.

Nope, its the part i listed, item number 24 sits in the self same place as the item he's discribing and does what he's discribing. The layshaft comes right through the case and the endfloat is taken care of from the cluster side, if the shaft has failed leaving an aparent blind hole then it would drift out on its own.

There are several engineering reasons for not fitting a gear that rotates on a shaft that rotates and only having a bearing on one side. I have a spare motor in the garage i'm going to pull the covers off tommorow and have a look/ take some photo's.

I would guess at, bearing has worn the idler has pinched onto the shaft the primary drive has forced it to turn while the layshaft has wanted to go the other way and its sheared clean off.

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thanks for the replies!

turrican64 --

i did set the float to the height spec'd by my clymer book (with the carb upside down, i believe it was 1" from the rim of the bottom of the carb to the top of the float, without the float needle's spring being compressed).

gear-wise -- can you please explain what you mean by 1 down 4 up (i'm a complete motorcycle novice)? are there 4 or 5 forward gears on this bike? i can't figure out how to tell what gear it's in -- i'm guessing you have to get it in neutral, where the bike rolls easily and then shift up from there. aside from neutral, i just can't tell which gear it's in at any given time. i understand about using the top of your foot to lift the shift pedal for some of the gears, but it's quite confusing for an utter newbie to figure out where you're at, gear-wise.

cynic --

i didn't mean that the gears are definitely not working (could be, but i'm not sure) -- it's more that, as a complete novice, i can't easily tell what gear it's in (i assume it needs to be in 1st to push-start it, since the kickstarter died), and the shift pattern's hard to figure out when you can't tell what gear it's in at any given moment. after the kickstarter died, i spent some time trying to push-start it, and i'd imagine you definitely need it to be in 1st gear for that to work, and i simply couldn't tell what gear it was in nor how the shifting worked.

regarding the kickstarter idler, i checked out that exploded view you linked to (thank you), and the part i'm talking about isn't in that view. it looked like that view was of the trans parts -- this kickstart idler is in the right side of the case, just to the right (as you're facing the bike's right side) of the main kickstart shaft (that the kickstart lever goes on), partially behind the clutch basket. it's a metal gear circlipped onto a short (maybe 1 1/4" long) shaft that slips into a needle bearing in a blind-bottomed hole machined in the right half of the engine case, facing toward the clutch basket. it apparently is for transferring the rotation of the kickstarter's main shaft (when kicked) to the primary driven gear on the back of the clutch basket. picture-wise, the case is closed up now, but i'll scrounge around & see if i have any old pics or can find any diagrams. it's really weird, though, how that stub shaft and the gear are free to slide in & out of the bearing a fair amount without any apparent method of keeping it more fixed in place.

thanks again for the replies -- i'd appreciate any further input.

To find neutral, press down on the lever several times until you feel that it won't go down any more gears. From there, it's half a click up into neutral. If you were to click up past the "half click point", then you would find yourself in second. Basically you click down from neutral to first, click up from first to second, click up second to third...so on so forth. I suggest you search youtube to see it visually. It helps sometimes.

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thanks for the further replies.

cynic --

it looks like you must be exactly right. apparently, shaft #14 in that first exploded view you linked to sheared off & left that odd stub on the outside of the gearcase. the inner end of the stub shaft did have a circular galled-looking spot on it, but i assumed it was simply from being spun while rattling around in that hole with the shards of an exploded bearing. and the other end of the sheared shaft really did look like the bottom of a slightly-weathered blind hole. i had wondered why yamaha had bothered circlipping the idler gear so that it could spin freely on a stub shaft that was already able to spin in the needle bearing (as opposed to the gear being fixed solidly onto that stub). crazy!

so i assume that i'm going to have to tear the whole engine case apart now & scrounge around ebay for another trans output shaft. oh well -- it's good to at least know why that 'stub shaft' thing seemed so odd, being loose in there.

i, too, thought it was weird, from an engineering standpoint, to have a shaft supported on only one end like that.

thanks also for the further info on shifting gears. just so i'm clear -- is it correct that you can shift the gears successfully while the bike's off & sitting still?

regarding the gas spewing out the carb vents -- i can see where a mis-set float level would cause it to come out the bowl overflow hose -- but would it also cause it to come out the other vent hose? if so, how do you set the float correctly? i did set it to the level spec'd by my clymer book when i had the carb torn apart (i don't have the book in front of me now -- i recall it being somewhere around 7/8" or so from the carb rim to the top of the float,with the float resting on the needle under just its own weight).

beyond that method, is fine-tuning just a matter of trial & error (taking the carb off, bending the float tang, putting it back on, trying it out, repeatedly)?

thank you!

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thanks for the further replies.

cynic --

it looks like you must be exactly right. apparently, shaft #14 in that first exploded view you linked to sheared off & left that odd stub on the outside of the gearcase. the inner end of the stub shaft did have a circular galled-looking spot on it, but i assumed it was simply from being spun while rattling around in that hole with the shards of an exploded bearing. and the other end of the sheared shaft really did look like the bottom of a slightly-weathered blind hole. i had wondered why yamaha had bothered circlipping the idler gear so that it could spin freely on a stub shaft that was already able to spin in the needle bearing (as opposed to the gear being fixed solidly onto that stub). crazy!

so i assume that i'm going to have to tear the whole engine case apart now & scrounge around ebay for another trans output shaft. oh well -- it's good to at least know why that 'stub shaft' thing seemed so odd, being loose in there.

i, too, thought it was weird, from an engineering standpoint, to have a shaft supported on only one end like that.

thanks also for the further info on shifting gears. just so i'm clear -- is it correct that you can shift the gears successfully while the bike's off & sitting still?

regarding the gas spewing out the carb vents -- i can see where a mis-set float level would cause it to come out the bowl overflow hose -- but would it also cause it to come out the other vent hose? if so, how do you set the float correctly? i did set it to the level spec'd by my clymer book when i had the carb torn apart (i don't have the book in front of me now -- i recall it being somewhere around 7/8" or so from the carb rim to the top of the float,with the float resting on the needle under just its own weight).

beyond that method, is fine-tuning just a matter of trial & error (taking the carb off, bending the float tang, putting it back on, trying it out, repeatedly)?

thank you!

Sorry i was correct, that sounds daft? but anyway.

Looking at the blow ups on csml the shaft is unique to the ct1, all the rest the CT2,3 DT's up to 76(ish) when they went to 6 speeds are the same which may indicate some kind of flaw with the design of that shaft back in the day. If it proves tricky to track down see if the later gear assy will swap. The engines are VERY similar, the only obvious difference to see from the drawings online is a circlip between 2nd and 5th gears. The gears are in the same order, in fact they are the self same gears (numbers match). I would imagine the later shaft would be massively easier to track down.

A company that has been very helpfull to me in the past is TY Trials they are highly likely to have what you need as they specialise in 70's-80's trail bikes, they will happily have a natter about your problem too.

As far as changing gears whilst the engine is off, its not really reccomended without a little caution as there is a risk of damaging the selector forks. That said if you just rock back and forth gently letting the bike move a foot or so in each direction it will allow enough movement for the gears to separate cleanly.

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