T-Max replaced primary Sheave

Since I got my T-Max I've been a bit concerned that its revving too high (compared to my last one). Its nothing I can be "sure isn't design" and its getting good fuel economy  ... but still 6000 RPM at 100kmh is too fukken much. So I decided to wait till the belt inspection interval.

In my last post about my T-Max I found something "amiss" when I went to check the belt (at the inspection time)

To save repeating myself I recommend reading that (short) post here.

Summary:

I think that the problem is that the weights are too light (and there is probably some misinformation about the standard roller / weight mass out there).

I think that the current situation (with the new parts) is pretty much "spec" but I can't actually know as a lot of this data isn't published.

Details:

So, in this post I wanted to just discuss some details about the work involved and to talk about outcomes.

Firstly for those who haven't done this, but are thinking of doing it, I'd say that its not difficult at all. Having had the earlier version (the differences I'll speak of in a minute) this newer system (which is about the same right through to the newest ones) makes the task of removing the weights (or rollers as the manual itself variously refers to them as) quite simple. The task of taking the primary sheave apart (making belt inspections a peach) is itself not hard.

There are a few points in the workshop manual (which I assume you have) that seemed more complex (perhaps only to me) than they were actually in fact.

The first point is the removal of the primary sheave, reading the manual (and some of the on line videos) makes it out to be a process which needs a special tool ... the sheave holder. If you have a decent "rattle gun" (or impact driver / wrench) then its actually totally un-needed to have the "sheave holder".

The trick is to not break the tension the secondary sheave has on the belt with the bolts as prescribed. The friction of the belt already in place (from the last time the motor was shut down) is entirely enough to allow the removal of the nut ... and thence pulling off the "right hand side" of the variator sheave to allow the belt to simply droop onto the axle of the primary sheave (which happens to be the engine crankshaft).

Its a peach.

The rattle gun I intended to use wasn't strong enough in practice (red rectangle) , but was in theory. I suspect that the previous mechanic put it on with too much tension. It should be tensioned to 160Nm torque and in theory my rattle gun is good for 215Nm ... it wouldn't budge so I borrowed this brute.

which undid it in about 2 seconds. My (smaller) rattle gun was used then to put the nut back on and (not knowing the exact tension it would deliver) just rattled it on "briefly" with the merest of "whacks" (NB not going spakko on it). I intend to check the tension later with a proper tool.

When you first start to pull the covers off the crankcase housing you'll see this:

This is actually the nut you'll take off and yes that's the crank (and yes mine looks like its been punished).

When you take the crank case cover off, you'll see it like this:

And its that spacer (or "collar" as it is mentioned in the manual) which takes that BT grease, the rest (only in a few places) takes "assembly lube"

As you can see that collar has holes (4 actually) and as well as the O-rings has a groove on the inside (which is obvious when its off) that you pack a little more of the BT grease into.

When you pull the crank case cover off you'll see that it has a bearing, which the "collar" sits in (and that's why it wasn't visible in the earlier shot).

This is the crank case cover removed and seen from the "back". The collar sits exactly inside this bearing. You can perhaps just see the two black lines where the O-rings rest inside the inner race. While the bearing is free to turn, the BT grease is just to ensure that the inner race of the bearing has a layer of lube between it and the crank "collar", and the O-rings ensure the lube doesn't get to the belt (a bad idea).

Now in the workshop manual its all a bit more confusing:

as well as all the instructions on what to lube and with what. 4 in the dotted lines there is here:

The weights I took out of my original variator were all within the diameter spec (25mm, min 24.5mm) given in the manual. However the manual doesn't specify weight. They weren't Yamaha ones quite clearly.

They were "Malossi" (and the previous owner swore it was all stock ... sigh) and while they had a few visible flat spots the should otherwise be good to go.

... except when I weighed them (on a scale that is only reading in grams) I found they were some 18g and some 17g ... when I weighed the bunch they were 143g (or 17.8g on average).

Interestingly the Yamana ones were on average 19.37g (or 155g for the lot) which as a whole mass acting on the variator is about 12g heavier ... which will mean that it takes a higher RPM for the mass of these to overcome the spring (in the secondary sheave) and mean a higher RPM before the "front" is fully engaged.

Taking a look again at the image of the primary sheave it was clear that the lighter mass resulted in the sheave never being fully in its highest gear:

as the red arrow is pointing to the maximum run out of the belt, and there is still a good centimeter of pulley left to occupy (again explained in the first post). This suggests that for those who favor weight changes to alter the power distribution in their T-Maxes it is akin to just riding around in a lower gear. Meaning your engine will be doing more revolutions per journey and thus wearing more.

So, with the new weights in the new sheaves I put the BT grease only onto  the thread, the back of the nut and inside the collar, reassembled it and took it out for a test ride.

This is where I found interesting things. I have (now) 4 data sets of RPM vs speed

• my first T-Max
• a fellow on the internet who sent me his 2009 T-Max data
• this T-Max before changing weights
• and this T-Max after changing weights

Here's what I found.

• my 2002 T-Max was much higher geared, doing 4830 rpm @ 100kmh (I bought an external Tacho for it that worked off the spark plug lead because it didn't have one) and the gear ratios seemed fully engaged (biggest it got on the front, smallest on the back) by about 100Kmh (sensible)
• the fellow with the 2009 model was doing 5100 rpm @ 60 mph (curse the USA for still being imperial) which is about 96kmh
• my current (2006) T-Max was doing 5800 rpm @ 100kmh (which is a fair bit higher than either of the above)
• after the rebuild of the variator it is now doing 5600 rpm @100kmh (which isn't much lower but is lower)

So where next?

Clearly I need to double check how much further the belt is coming out along the variator at higher RPM, is it making it all the way out? I also need to pull the rear sheave off and see if there is anything amiss there (and I still don't have any explanation for what caused all that damage to the inner sheave).

However I'm thinking that "perhaps its just different" ... I mean its getting good milage (4.5l/100km (or 52US miles / gallon)) and there are differences in the models. For instance:

• the 2002 model developed peak torque at 5500 rpm (a bloody smart location really), while my model develops it at 6250 rpm (marketing wankers involved I'm sure). This means that to keep the cruising speed (assuming highway use) close to the peak torque they'd need to move the rev / gearing ratio. As it happens its almost at the 5500 revs of the older motor and probably within 90% of peak (its a not a steep curve) right now.
• Opening the throttle sees the rpm rise quickly (faster response than my older bike) to over 6000 which is getting near to where this motor develops its peak power
• Peak power has been moved from 7000 rpm on my 2002 bike to 7500 rpm on this (the 2006) bike

Its quite likely that the lack of publication of Yamaha weights has led people to perhaps measure the early model and then not double check that the parts haven't changed.

Perhaps too, the change from Carburetor to Fuel Injection (and some years of service experience) has led Yamaha to decide that slightly higher revvs isn't bad for the motor?

The older model

Having had both now (and serviced both now) I can say that one of the steps backwards to me is the variator. The older one was much more robust in design and was actually well lubricated (while this one is dry). Lets take a quick look at the older one from the manual:

Things to notice are:

• heaps more sliders to stabilise the sheave to the cam (as the outer sheave is not actually attached to the crank and relies on the internals to prevent slippage)
• the weight rollers are deeply embedded in a bath of BT grease, so really are massively protected. I never once had any problem in 160,000Km of daily riding (including traffic, dragging cars at the lights, mountain roads and touring)
• the whole thing is easily kept into one piece when inspecting and changing belts, and indeed being a bit smaller I never needed to take it off to change a belt (unlike the newer one).

Note in the assembly instructions just how much grease is involved...

so as you can see even when you remove it, that sheave does not "fall apart" in your hands (as the newer one will when you remove it if you don't keep a good grip pressing the parts together).

Combined with the more relaxed rpm range of the older one I feel that Yamaha has bowed to the "wanker" set (I mean, they've got the money right?) and taken the T-Max from a practical and comfortable general purpose motorcycle towards a "wanker bike" when the reality is that it can never be an FZR-600 (and if you want one of them you should get one).

The removal of the fantastic and practical and discreet tie down straps from the passenger grab rail (I've loaded plenty of cartons of stuff onto the older one as a real work horse) and the increase in this direction of the newer models says that even more loudly.

Conclusion

So looking now at these numbers perhaps it really is all back to standard now.

Anyway, when my sheave holder arrives I'll need to pull the crank case off again and check that the rattle gun put the right tension on that nut (it was a guess, but it can't be more than 215Nm because  that's all its good for, and who knows how accurate any torque wrenches actually are anyway) and I'll be able to inspect (after run in) how far that belt is getting up along that sheave.

I'm impressed with just how reliable and robust the T-Max is, having done 160,000 on my first one (most of that being my mileage) and now having this one with 107,000 (and I've only done 13,000 of that) I see that belts last well, maintenance is straightforward and they can tolerate an amount of shit without breaking. I seldom got 20,000 km out of a "chain and sprockets" on my bikes, and with belts being less work and about the same price its quite encouraging.

more as it comes to hand ...