Friday, 13 July 2018

T-Max using my new sheave holding tool (and fitting a new belt)

This is essentially part 3 of a series

  1. identification of a problem
  2. replaced the major part

So this is sort of finishing off ...
When I did the work on my T-Max back a couple of weeks ago I didn't have a sheave holder to hold the sheave (pulley) but instead got it off with an 18v electric rattle gun. Now as I mentioned in that post I didn't know what the amount of torque that the rattle gun would be (although the maker says it's good for 215Nm (and the manual says 160).

So this post is about double checking that and providing a few observations missing from my previous post as well as some significant changes to my measured RPM.

New Sheave Tool

Normally I'd have "munged up" my own but after moving out of my old house I just don't have the workshop setup to do that right now so I decided to buy one. Having seen some ones on YouTube bend I was cautious, but I got this one off an eBay seller in Greece (not China) called f1sport (link to his profile) and while it worked out a bit for me (in Australia) I think the price is totally commensurate with the quality as its about US$83.

Here are some pictures I took of mine, its simply an amazingly high quality bit of steel

Basically all the bolts were in an included bag, and you need to assemble them ... given you're clearly mechanical buying anything like this the lack of instructions are more of a pat on the back of your intelligence than an omission.

The steel is impressively thick

Todays work

So with the variator held by the sheave tool tried using the torque wrench (set to 160Nm) to see if it tightened any, it didn't (setting off the small "click" in the head). So I loosened the nut, and then tightened it with the torque wrench and then tried to undo it with the rattle gun. Unlike last time, this time it did undo, it moved very slightly at first (if you weren't looking you'd be forgiven for thinking it wasn't moving, it took a few seconds of "rattling" before it was starting to move at a pace where I knew it'd spin off fast soon.

Basically I'm now confident on how much torque to put onto the nut with the basic electric rattle gun and have it pretty close to right (and lets face it the torque wrench isn't calibrated anyway, so there's bound to be error), which is what I did 2 weeks ago (and it seems I was on the money anyway).

So now I know.

The other purpose of todays exersize was to pull the belt off and put my new one on. I didn't do that last time because the surfaces of the new sheaves looked a bit rough (not polished) and so I was wanting to let the old belt "polish that in" for me before putting on my new belt.

This gave me the opportunity to have a look more carefully at the secondary sheave (which I didn't do last time) and see the extent of damage that may be there (as less was visible the way it was). While I didn't like what I saw, it wasn't as bad as the primary suffered.

Unlike the primary, the secondary suffered its impacts much closer to the center with just a few hits further out in the sheave ... this is consistent (in my view) with the "hard bit of shit" getting in there at highway speeds (where the wrap of the belt would be tight to the center at the rear and out on the perimeter on the front sheave.

Indeed a closer look makes it clear that some parts of the interior have not seen the belt yet as the dings are still rough and not filled with rubber dust.

The red arrow points to dings which seem to be sitting on the highest gear point of the belt, the green seems to have not seen the belt and I think the blue is the boundary.

I decided to put the new belt in and when I measured the older belt I was surprised to find it was significantly under spec. I'm sure that when I put the new sheave on that the old belt was 31mm, however when I measured it today it was 27, or at about 3mm below tolerance!

So I don't know if I did measure it properly or didn't ... vexing.

With the new belt installed (and knowing it was thicker) I took it out again for a ride and observed the rpm speeds with this new belt (and of course the installed 2 weeks back 19g standard weights). What I got makes me wonder if I indeed failed to measure the belt (or look properly at the vernier).

So now at 100km/h my tacho is showing (about, its not digital) 5,250rpm (more than 5200, less than 5300) which is actually much better, and closer to what my stock 2002 model was doing (which was 4830 and I had a digital tach fitted to that)

It goes like this now:
speed revs ratio

60 4000 66.67
70 4300 61.43
80 4500 56.25
90 4870 54.11
100 5250 52.50
110 5500 50.00
120 5870 48.92

With the "ratio" being how many revs per km/h, showing that the bike is now giving lower and lower revs per speed as gearing increases.

This data also shows that I clearly can't have measured that belt properly because

  1. its unlikely that it could have stripped off 3mm of belt in 2 weeks without there being a mess in there
  2. I further dropped the revs as I got it it was 5,800 @ 100km/h, after the weights it went to 5,600 and today with the new belt to 5,250


This is the data for my old 2002 model (previously discussed)

speed revs ratio

60 3740 62.33
70 4080 58.29
80 4250 53.13
90 4520 50.22
100 4830 48.30
110 5340 48.55
120 5800 48.33

which now looks pretty close, although the older sheave seems to be fully engaged much sooner than the new one. I did a video today (forgot to do one on a fortnight ago) and interestingly my observation was that the weights overcome the spring to fully engage the front sheave at about this rpm.

As it happens I have a theory on why its later to engage. The answer can be found by looking a bit further around the fixed side of the secondary sheave at the spring

which is BLUE !

I'm pretty certain that Yamaha don't colour code their springs which means it (like the malossi weights) are after market.

Looking around on eBay  I see that there is indeed a company making blue springs, but its not Malossi as their springs seem to be Red (+30%), White (+13%), Yellow (+7%) and Green (-39%).
The company selling Blue is unclear about it because their kit also comes with some other adjusters to allow you to increase the spring tension  more.

This then is consistent with modders without a clue because putting light weights in with heavy springs will restrict the engine to a narrower rev range (never getting top gears) and be super revvy (when the engine was designed to be super torquey).

I guess that the next things on the agenda are:

  • keep an eye on the belt wear and see of those marks are causing it to wear faster (and the heavier spring won't be helping)
  • I still have no idea what caused the damage, so perhaps its pull apart the secondary sheave and have a good look. I'd have done that today but I didn't have a 27mm socket which would fit

Given that its got relatively high mileage and an unknown service history its probably a good idea just to pull that secondary apart and give it all a lube up...

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