Chunkstyle

hi guys -- i'm a novice working on rebuilding the engine on my old ct1 175 & was wondering if somebody could please answer a couple questions: 1. while i've got the case cracked, i'm also replacing as many of the bearings as i can, as insurance. in the crankshaft area of the case, water got in so that there was sludge in there that rusted the left side crank bearing somewhat. since the lower connecting rod bearing is in that same area and down low, i'm wondering if i've got to replace it as well, even though it's not easily removable. it doesn't look rusted, but it's hard to see it well, between the crank counterweights, and there is some rust on those weights nearby. and i figure that it's probably one of the highest-stressed bearings in the entire engine, so i don't want to skimp on it. if i do need to replace it, how bad a job is it to press out that pin & reassemble everything? my clymer manual seems to show it as a pretty big/precise deal, with v-blocks & dial indicators & alignment tools, etc. 2. when i was splitting the case, with a puller threaded into those holes behind the magneto, it took a little more pressure on the puller than i expected and a lot of tapping of the case halves to get it apart. the clymer manual said just "hand pressure" on the puller. and now that it's apart, it looks like the crankshaft bearings are possibly a press-fit onto the crank. is that supposed to be the case, or is something messed up here? and how do i get the case back together while having to press the case halves-with-bearings onto the crank? it took some pounding with a brass hammer to drive the crank out of the left-side bearing once the halves were split. thank you for any help or advice you can offer! drew j.

hi guys -- i've got an old ct1-175 i've been working on, off-&-on, for a few years with my son. the time has come to pull the cylinder & check its diameter, to see if the cylinder needs boring oversize. if someone could please answer a couple questions about this, i'd appreciate it. 1. i don't have an inside mic nor a regular mic big enough for the cylinder diameter. i do have telescoping gauges and a pretty good mitutoyo vernier caliper. would the caliper work & be precise enough for checking the cylinder? 2. the odometer reads 2145 miles. is that really low mileage for one of these bikes? i've got this hope that, possibly, the cylinder will be largely unworn. this is my first motorcycle, though, and i don't know anything about typical mileage & wear on a bike. 3. similarly, is there a decent chance that the main bearings in the engine & trans would be good with this type of mileage on the bike? i've already spent more $$ than i'd like nickel-and-diming on various parts for this bike, scrounging on ebay & such, and don't feel like shelling out more for bearings. on the other hand, though, with the engine split open, now would be the time for the extra insurance of new bearings. thank you for any help anyone can offer. drew

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!

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.

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!

hi guys -- i'm hoping to try firing up the old ct1 175 my son & i have been working on, that i've posted about here a few times (thanks for the help, by the way!), and i'm such a complete novice regarding motorcycles that i'm not sure how you properly fire one up. i'd like to get all my 'ducks in a row,' so as to avoid stupid mistakes. here are the things i'm aware of (most, if not all, are probably incredibly basic to you guys): ignition switch on petcock open fuel in tank look to see if fuel flows down hose to carb (it's a clear hose) transmission in neutral tires aired up choke knob pulled out oil in gearcase 2-cycle oil in autolube tank is there anything i'm missing? do you have to have the clutch lever pulled when starting if it's in neutral? and does the battery under the seat have anything to do with starting, or does it strictly power the lights only? thank you!

thanks again, paul! hopefully, we'll be able to try firing it up within a couple days (then we'll find out what else needs work on the bike, that we weren't aware of!)

thanks for the reply, paul. do the open-ended hoses on the 2 carb vents need to go uphill above the carb a certain distance before heading downward -- to make spillage more difficult? my friend mentioned something along those lines, but i'm unsure if that's correct or not. thank you!

hi guys -- can anyone please tell me what these 2 ports on the carburetor (marked 1 & 2 in the pic) are for, and what is supposed to be connected to them? a friend thought they were both vents of some kind & just needed an open-ended hose "whip" attached to them, but he wasn't positive. the fuel inlet line is on the other side of the carb and a much bigger barb. any ideas? also -- is the plastic fitting marked 3 in the pic some type of crankcase ventilating elbow (akin to a car's pcv valve) & the hose attached to it is supposed to be left open-ended? thank you for any info you could offer.

hi -- i'm a newbie to this site, as well as to motorcycles in general. this past spring, i bought an old 1973 ct175 fairly cheap (missing some parts & needing work) from a neighbor down the road, intending to fix it up with my son as a father-son project. never owned (or ridden, for that matter) a motorcyle before. after much time on ebay, on the phone with our local yamaha dealer, scrounging parts & figuring out how to cobble stuff up, we're getting fairly close to trying to fire it up for our first time. one question, though -- on this bike, there are no markings on the keyswitch that indicate what the key positions are for. it seems as if there are 3 positions it can be in. can anyone please tell me which is 'off,' which is 'run', and what the third one is for? are there by any chance pdf's of the owners' manuals for these available anywhere, or are there still under copyright & not available in that form? thanks! drew joseph