xs750 build step by tedious step, "build-along" with me

I thought I would pause from all the 5th gear stuff for a bit and bore out my cyl. the 83mm boring tool says 70 rpm, so I set to drill to slow.View attachment 166442 View attachment 166443View attachment 166444
i did the same thing but after measuring I chucked the hole saw in my cordless and ran it against the wet grinding wheel for 23 seconds, PERFECT fit. I'm picky so chucked the hole saw in the drill press, followed up with fine sand on a damp wadded up shop towel for the final finish.

ichiban.jpg

5 sticker rated!
 
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thank you so much twomany.... i read everything there, gonna go blind now i think...lol
I will be making some posts this weekend about where im at with the build.
I do know there was no undercutting on my mikes 5tth overdrive it looks good in there.....

Two many, Im curious if you mentioned
 
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And another for the OD 5th gear, do a forum search on "involute" or "diametric pitch".

two many I read all those articles ,except I didn't search for the info on involute, or diametric pitch, maybe today. but Im curious if you think that the tooth profile is different on the mikes gear as to mesh differently (or more proper) .... do you know of anyone that has run mikes 5th with the factory 5th, and if you do then did it FLY? as in was it ok, 69 bucks for 5th overdrive but to purchase both 140.00 kind of rich for my blood, I want to spend more money on valve adjusters and such,, like I siad i did take a very close look at my 5th gear and the surfacce you said to look for undercutting is smooth as smooth can be



question 1 , anyone run 5th with factory fifth?
question 2 , if so was it a 77 earlier or 78 gearset? (78 marked with one and sometimes two groves around the outside of gear teeth
 
I recall that most here that have run the OD 5th just kept the original mating 5th slider. Seems that the gearface geometry of the slider is the same as the MikesXS 5th. I believe that MikesXS suggests buying theirs because it has fresh gear faces, reducing wear in the new OD 5th.

Here's the service bulletin for the '77 transmission change.

77-04-29_M023-01_ChangesToSpliningTransGears .jpg

77-04-29_M023-02_ChangesToSpliningTransGears.jpg


Essentially, only the splines changed, not the gearface geometries...
 
to many xs1s ... Im going to try and get a better photo of the mikes gear vs the factory 5th, and even 5th slider, they are not the same gear shape whatsoever, one is like a square ...strait up on both sides then an angle half way op and a flat top, this is the type with a grove cut around it.... being 78 and later...

I see the post of the diferent internal diferences, but im also under the understanding that the tooth shape changed in 77 or 78
 
I got this from a uk site called smedspeed
the Yamaha XS650 gearbox is a robust design, a vast improvement in terms of the selection and quality of manufacture compared to its contemporaries. It was improved somewhat when Yamaha changed the gear tooth shape in 1978 to a more rolling design. By increasing the area of the gear tooth in engagement at any one time, it decreased individual tooth loadings. To differentiate the old and new tooth shapes, Yamaha machined a shallow groove around the periphery of the gea
 
gears2.jpg
http://www.smedspeed.co.uk/tech.html

about halfway down the page he talks about the gears, he is refering to the outside tooth of the gear , I belive???
I have about 6 transmitions, but only the ones with the groves around them, and none of them look like the shape of the mikes tooth shape
thats why im wondering if the mikes gear fits the pre 78 tooth desighn OCD of mine here seeing every posibility
its hard to see in the photo but one tooth desighn is much more "quare, compared to the rounder one
 
Well, good, you're knee-deep into this mystery.
I don't have the equipment to accurately measure gearface geometries.
All I can think of is to make molds of the various gearfaces, and see if they match...
 
Is it worth all that extra work when you could just buy the extra gear from Mikes and be done with it, assuming there is no machining required to properly fit on the shaft? That is, unless you are in to spending time doing all the measurements and comparisons for the sake of curiosity. Both gears I purchased from Mikes fit perfectly. I read all the previous threads on people having to machine to get it to fit properly, and knew it was a gamble, but the ones I purchased fit perfectly and so far it has worked flawlessly. Granted, I have less than 1,000 miles on the motor since the rebuild, but so far so good.
 
In relation to the gear dogs, from the German XS site, (use google translate).

http://www.xs650.de/forum/viewtopic.php?f=1&t=28908&p=275861&hilit=5.+Gang+rad#p275861

Apparently there is a relief missing on the dogs on these gears causing them to jump out of 5th.

I'll see if i can dig out more info on the meshing at some stage, I vaguely remember coming across it, however I am in the middle of exams at the moment so don't hold your breath.
 
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2XSive, that kinda what my thread here is all about, 750 build step by tedious step, and maybe im going of the deep end but its the curiosity thats got me going, I know that when the "colective" get to gether and we all exsamine a subject from our own unique perspectives that the learning cure gets shorter and we all learn something, new , my thread is about checking all the tolorances step by step and finding new things to look for when building an engine, ive built many many engines and I allways have fun, but this one (tempted as I was just to throw the top end on a known good bottom) this one I wanted to go all out on, not all out as in "gold card spending spree" but all out as do all the little things you can do yourself like tightening up the tollorances on a stock oil pump or adding oil jet sprayers to the case for more oiling,. its not that I dont want to just get the mikes gear and say fuck it, I want to know what makes a 74 thru 78 gear tooth shape differnet from a 78 thru 84 gear tooth shape, and belive me after a few days being stuck trying to find the answer, and I have been to every corner of the internet, after a few days I was tempted.. but alas what would a tedious step be with out finding out what was aat the end of the tunnel... JA KNOW?

i guess what im saying in I aprecitae any and all input, and even the recomendation to get the other 5th gear from mikes, but what if I do finnaly find out that the mikes gear is a mtch for 78 thru 84, and those that have had a noise is due to it being a 74 thru 77 gear... or vise versa, Im hopping to find that answer, well unless I go blind from staying up on the computer till 430am lol.. wouldnt it be nivce to say once and for all, the mikes gear works with "such and such year" and not with the other, (that asuming smedspeed in the UK is corect and yamaha did change tooth desigh, I only have 6 transmisions and there all cut with the grove indication there 78 and later... so I havent a 77 and earlier to compare the mikes to, But Im curious why mikes originaly sold them for 78 up, makes me think they work with the later gears. oooweee long winded today sorry kids.. a little more reserch and I will move on, I will do the "paint test, but with prussian blue since I have it on hand for setting up rear ends in cars
 
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I'm sure your research will pay off, especially for anyone else considering 5th gear overdrive. Wish I had your patience and curiosity, lol.
 
ok kids, this is what I was originally trying to figure out, you dont need google translator to see what beno was talking about here since they have excelent drawings of the problem, anyone interested in this should at leats take a look at the link to see whats being discussed, this is where the dogs fit into 5th gear, weathere it be factory yamaha or mikes overdrive, NOTE: even if you buy both mikes gears, if this is indead a problem than having both mikes gears will still not solve this, the gear with the dogs is third gear, it sits next to the 5th gear overdrive and third gear dogs go inside the mikes gear dog holes, so Im back to finding out a way to measure the deep part of the dog holes and see if they in fact do have a "tapper" or relief cut as benno described it a few posts ago,

almost every part I need to asemble this build are sitting on the kitchen table so believe me, Im ready lol, but as I said what would a tedious by tedious build be if I just said fuck it and hoped for the best, Im a perfectionist and most like compulsive (or so I have learned doing this thread) and Im gonna try my best to sort this out for myself and everyone who ever wants a 5th overdrive, But mostly me :geek:
 
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