SRX600/XT600 5th gear input shaft pinion wear!

[themoudie]

A couple of images, if people haven't seen it afore, of characteristic wear of the 5th gear pinion on the mainshaft (input shaft) of SRX600 and XT600 gearboxes. There was a manufacturing issue with the hardening of these pinions that was supposed to have been resolved.    However, you can see the pitting and fretting of the teeth surfaces, which is variable and the extension and bruising of the drive face of the 3 driving dog slots in the side of the pinion. Lugging the motor in 5th gear aggravates this problem.

This pinion came from the XT600E motor that I am rebuilding at present and requires the use of a press to remove the 2nd gear pinion, so that the 5th gear pinion can be removed. The whole lot then has to be pressed back together and the 2nd gear can 'jump' during this process, so that the critical clearances between it and the 5th gear pinion and the overall width of the gear cluster on the shaft are not met. This means that the process of stripping and re-assembling has to be repeated! 

Costs at present are ~£55-00 for ther pinion + 1 hours labour + carriage +VAT so no change from £120, so just be aware when buying Yamaha 600 singles!

Slipstream Tuning did the job for me. 

My regards, Bill

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[Steve Lake]

hey Bill, I'm thinking that £120 for a proper job (a Cornish phrase ya knows... and a decent pint), isn't too bad.

however, it's not why I'm here, what I'd like to know is.... what are the symptoms of 5th gear wear (I'm the lucky individual, who, having owned, rebuilt & sold 7 srx6's... never had a 5th gear problem)..... but.... today .... on my way home from work .... I noticed , through the pegs and my arse (the main feedback areas for any discerning biker :-) ), a sort of 'grumbling' in 5th, tends to disappear after 5500 revs..., it's akin to chain 'lash' on a really loose chain (which it isn't),
I've always taken the bike up to 5000 revs in 4th before changing to 5th... never chug along at 50mph in 5th..
For an srx6 with a bit of tuning (head work, bored out to 639, carillo rod, high comp piston, twin 33 dellorto's) it is and always has been a remarkably quiet engine... and remains so...
as they say .... ideas on a postcard please ...

pip pip

[themoudie]

Aye Steve,

"Proper job!" alright, but when you start adding up the pennies for a full engine rebuild you'll not see any change from a grand!  That is with me doing all the stripping, cleaning, measuring and then building. If you were to pay somebody to do a full job then I suspect there wouldn't be much change from 2 grand! 

As for your rumbling/grumbling through the pegs and posterior, I have noticed that rough chip road surfaces often give that sort of feedback as can cream crackered wheel bearings. There are two other things I would "wonder" about! Have you got a grumbling crankshaft main or has the generator flywheel started to fret on the taper? Both can be harmonic/rpm related and smooth out as the revs rise and torque action reduces; if you know what I mean? 

Another way to check would be to take one of those thin, telescopic magnetic probe/extractor tools and after leaning the bike to the right or at the next oil change, stick it into the sump via the sump drain plug and drag it about, you may or may not find either bright shiny bits of fretted steel or black magnetic sludge, I doubt the latter with you! There is no need for me to teach you how to suck eggs if you find magnetic bright shiny bits! 

That all maybe a load of old cobblers, but it is only when the teeth start to fracture and come off the pinion that you notice notchy drive and very weird gearchanges!   

I managed to shear 5 teeth from the 2nd gear pinion on the mainshaft (Input) of my Duke 450 in 1977 on the Island that proved very lucky, expensive and felt awful. Slowing up for Signpost, with town traffic, came down the box and noted that 3rd to 2nd was a bit notchy and drive wasn't constant. Rode the bike round to my friends in Onchan, with gearchanges increasingly difficult and drive noisy and lurching in 2nd. Dropped the oil and we were greeted with lots of shiny slivers of steel and after using a magnetic probe extracted the 5 teeth through the sump drain plug hole. Luckily none of the teeth locked the gearbox or bearings and no scoring to the barrel and piston.     Needless to say a complete strip and new bearings throughout were required. 

My regards, Bill

[Steve Lake]

Thanks Bill, all good stuff, and will check all the things you mention.... I'm of the opinion (like you), that it could be the l/h main/generator area.... only 'cos 5 years ago during last rebuild I used Loctite bearing fixative as was worried about the bearing being too 'easy' in the housing....
so, bit o f a dilemma, do I rip #1 apart before I go to the 'classic' tt, or take a flyer on it ... 
#1 son is heavily involved in #5 refurb.... amazing how .... a bike that has done just over 1000 miles in the 8 years since we sold it, can have so many things wrong with it....

AND.... #1 let me down today.... well, not #1's fault really, half way to work, spluttered to a halt, didn't seem to be petrol (lack of)... and nothing obvious externally... so pushed 400 yds to Tesco fuel station, and bunged in 10 ltrs of their finest, one kick and we were in business .... for a mile or so.... then died, bugger!!.... phoned work told them I'd be late.... thought about ringing Flux insurance and using my recovery option, but... well it seemed to be admitting failure.... hell I know every nut & bolt of #1... so booted into life again, and in the mile and a half I got before the next unscheduled stop I'd figured it must be fuel... so pulled the feed off the twin dellorto's, a feeble dribble, (I use 2 inline filters, one in the main and one in the reserve feed), pulled off pipes from filters, nowt from main, loads from reserve, so plugged reserve into carbs and bingo.... 20 mins late after a lovely thrash down the A47.

good bike shop 200 yds from work, so picked up 2 new filters , handful of pipe clips and some new pipe as well.... weekend job... drain tank and clean, drain carb bowls and clean, fit new filters/clips/pipes.

now.. as you are the font of all information Bill (some of it useful  )....  where can I get a fuel tap service kit? .. used to see them on fleabay but not now...
and.... is there still a needle/jet/spring tuning kit for the standard Yamaha carbs available .... another thing I used to see on fleabay but not now... could do with one for #5.

have a good weekend Bill

pip pip

[themoudie]

Aye Steve, I shall try to take things in the order that you set them out and then I might fling some at you! 

At present I am trying to suss a method to pull my XT600 crank back into the crankcase, without the factory puller and accessories; it is a wee bit 'tight'! Whereas, when I put Sally (1JK SRX600) together, the bearing and crank fell into the housing with hand pressure!    So far, with about 75K Km since the rebuild I haven't had a problem with it. As for a strip down afore the Manx? It would be a real bummer to have a good motor let go afore or whilst enjoying the festivities. I would be tempted to take the nearside outer casing off and maybe even the generator rotor, then you can swing on the end of the crank if necessary and see if there is any movement in the crank within the bearing or the bearing within the housing, as well as checking the contents of the sump.

Sally can be a real mare when it comes to fuel starvation. I think that the vacuum isn't as good as it might be and consequently when running on a constant throttle at revs over 4,500 she gets the 'Skippy' syndrome! Turning the tap to the 'Prime' position soon sorts things out and with the odd backfire normal service resumes. I too use big fuel filters and a 60ml syringe with a tube and rubber sleeve ( they're used to feed lambs directly into the stomach and also back bleeding brakes using the vacuum method!    ) to hoover the sludge from those tank wings, but if you have that feed to the carbs from lower in the tank wings, rather than the original mid point of the underside of the tank you are less likely to have the sludge problem.

Fuel tap service kits can be obtained from NRP, here is the link to the page on their website: NRP_SRX600_1XL_or_1JK_fuel_tap_kit  SteveH and others have used their kits and recomend them.

As for the carb tune up kits; Dynojet maybe what you were looking for? Here are 2 links to potential suppliers in the UK: Road_&_Race_link also PDQ_link

That seems to be everything in order and I'm off to sheet alley after a wee 'Leapfrog'; tomorrow a canter afore the tempest arrives from the west, that'll cock up the first day of TT practise! Then maybe a little crankshaft drawing!    So how did you draw your crank into the casing? And, any chance of an image or drawing with some dimensions of where you have your fuel feeds from the wings of the tank of #1? 

Good health and an Abbott! That #1 a bit o' a doxy!

My regards, Bill

[Steve Lake]

ahhh ... the good old laphroiag sleeping tonic ... works a dream (geddit ?  )... didn't have to use any force on removal or replacement of crank assembly .... thinking about it... it was 10 years ago I did the strip down, and 5 years ago it was done by Roger Cotterell at Denver Motorcycles... as I'd run out of time, that was after I'd had a 'pinch up' and had to have the final rebore, new piston and it was when the carillo rod was fitted and of course a new beefier oil pump... for a tad under £500 folders it was a very good deal... I thought.

enjoy the weekend Bill
pip pip