Malaguti Spidermax - I am so screwed

why you should not work on a warm engine

2014-8-26
2011-5-4
With the gas prices high as they are now, I wanted to try to find a way to lower the gas consumption of the MASTER engine from my Malaguti Spidermax.

Since adding to the 2mm washer (between the driving pulley halves) brought the rpm up reducing the washer must bring the rpm down.
And with lower rpm might come a lower gas consumption.

So much for the theory.



To test the max difference possible, I removed the 2mm washer (pictured) completely.
Then just pressing the belt into the driven pulley a bit (first mistake) I screwed the 27mm nut back on, fixed her with my trusty impact wrench, turned the pulley a bit and screwed a couple more seconds for good measure.
On the test run the Spidermax behaved like the original 8 roller setup and I did not see much lower rpm in the low and medium rpm band.
The experience was that bad that I did not care to try a 1mm setup.

Back home I after just a couple minutes rest I tried to get the 27mm nut off from the still very warm engine. That was my second mistake.

So far I took the transmission apart over 30 times and except for shearing off some of the thin low quality bolts which hold the transmission lid in place I never had any trouble with any part of it. I always check the bolts and nuts for wear and tear to be on the save side.

The impact wrench normally loosens a screw within a couple seconds, but after 10 seconds nothing happened. I tried for a few seconds more until the impact wrench got hot and the grease in the impact part started to come out of the wrench. I decided to let the engine and the nut cool off and tried later again. The nut moved a tiny bit but it took me a long time and several times to reverse the wrench (like rocking a car out of the mud) until I finally got the nut off. While trying to keep the pulley fan wheel from moving I managed to break off one of the fins.

After getting the nut off I discovered to my horror that the nut had been fused with the pulley axle and both threads were completely destroyed.
Oh happy day!

Now I have 2 parts what have to be locked together and they lost their ability to do so. The nut is easy to replace... It just took me several days, more than 10 hardware and bike stores and a 100km round trip to find one.
It is easy to find a 27mm nut but they normally come with a 2.5mm thread. This nut but has to have a fine thread with 1.5mm. M18 1.5mm / 27mm is what you need.

Now my problem is where to screw it to?

you see in what sorry shape my old nut is

My options are either to remove the two washers what normally distribute the pressure from the 27mm nut to a bigger surface of the fan wheel and hope that the remaining 5mm are enough to hold the wheel in place without causing any problems or to cut a new thread into the axle.
The problem with the second solution are higher costs and how to keep the axle from turning while I cut a new thread. Since this involves some major torque and I see now way to keep the axle secure from turning I opted for solution one for now.

since I messed up one fin and the wheel has 19 of it I needed to nibble some material of the other side to keep it balanced.

The first test ride was without incident and if any problems should occur I will post it here.

2014-8-26
Over 3 Years, ca. 25.000 km and several times removing the nut, installing new rollers or sliders and re-tightening the nut later everything still works without a problem.