Derbi variant piston port rear pulley mod pics

Didn’t find any posts about modding the derbi piston port rear pulley so this is what I did.

Turned the steel hub down to 1.5mm and took down the movable cheek a few mm too.

That’s it. Not hard

Now I have quite a bit more variation travel and I totally screwed up my tuning so I gotta start from scratch. Oh well

A35693E4-B101-428F-A159-F0C130512FDB.jpeg

(edited)

Re: Derbi variant piston port rear pulley mod pics

ah yes, the best mod ever!!! There's also the pyramid reed ones that are less restricted in the outer cheek that don't have that huge lip on the inside. This plus using the ramp plate spacer on your stock or tjt vario will make you go fast on a pp/pr.

https://www.treatland.tv/ramp-plate-SPACER-for-droppin-your-belt-2mm-p/ramp-plate-spacer-ring-2mm.htm

Without bringing the cheeks together as much as possible, your belt will prob slip with the spacer. Here's a pic of after i did mine (my belt sat below the top of the pulley before:

IMG_20201214_212848.jpg

Life changing!!!!

Re: Derbi variant piston port rear pulley mod pics

if only there was a bigger rear pulley and like a 18.5 or 19 mm belt for us pp boys :(

Re: Derbi variant piston port rear pulley mod pics

Haha yeah I used the spacer too but had to shim the vari out a bit (floating fiber washer on boss) between vari and ramp plate) to grab the belt better.

I have 16s so I really have to gear up custom style.

Re: Derbi variant piston port rear pulley mod pics

After doing this on mine the rear pulley bushing kept pushing itself out, causing it to get stuck open. Found a flanged bushing at ace, ground it down a bit and that solved it

FB_IMG_1608043280904.jpg

Re: Derbi variant piston port rear pulley mod pics

Brandon Weiss (Detective brandon to you) /

I had my PR pulley turned down by Ed's mopedshop, he did it the same way! I haven't had a chance to test yet.

I wonder if having the spacer and turned pulleys will make it noticeably harder to start with a one way bearing? You're effectively reducing your rear wheel's mechanical advantage over the crankshaft by doing so. (It increases the mechanical advantage of the crank over the rear pulley/rear wheel, but the advantage is reversed when the roles are reversed).

Re: Derbi variant piston port rear pulley mod pics

It’s harder to push the bike now with a 2 way bearing

Re: Derbi variant piston port rear pulley mod pics

Brandon Weiss (Detective brandon to you) /

> JBOT Admin Wrote:

> -------------------------------------------------------

> It’s harder to push the bike now with a 2 way bearing

Makes sense, so that definitely means starting it with a one way bearing will be a little tougher. Only way to know for sure is to try it i guess

Re: Derbi variant piston port rear pulley mod pics

It's fine. I had the cut down pulley on Gila pp with one way and it was no problem

Re: Derbi variant piston port rear pulley mod pics

damn, i didn't know why starting my bike suddenly became harder but now it makes sense lol. I run the one way and it's def noticeable for me. But i do have a decomp head which helps out just enough to start it.

Re: Derbi variant piston port rear pulley mod pics

Tweaker trash /

Ur guys are crazy about getting those belts to run a few mm higher or deeper

Re: Derbi variant piston port rear pulley mod pics

I did some tuning yesterday and actually removed the spacer and then it’s respective boss washers to take up slop. The bike acted shitty down low, with a quick slip then engagement (which actually slowed acceleration) When the belt was not totally as low as it could go up front, the clutch hit and it was instant engagement. So I reversed it to go back to instant engagement.

It would be worth doing if I changed gearing to be taller but I wasn’t in the mood to fuck with gearing as well. Another day maybe

The pulley mod was worth it though as the belt rides higher in the rear pulley still, so more variation travel

Re: Derbi variant piston port rear pulley mod pics

Brandon Weiss (Detective brandon to you) /

So it's worse with the plate spacer? Is that because it moves the plate out farther than the extra bit that the modded rear pulleys close and you lost belt tension? or is it because the gearing was just too low and it slipped the belt (edited)

Re: Derbi variant piston port rear pulley mod pics

I think the clutch is slipping. The belt was tight in the vari.

I think the gearing was just too low at that point and the clutch slipped due to the increased resistance which doesn’t make sense to me logically but it is what it is.

Bike was much harder to push with the belt like .5mm off the boss. So it’s riding higher now and just engages and feels better.

Changing final gearing might change this idk

Re: Derbi variant piston port rear pulley mod pics

Tweaker trash /

Re: Derbi variant piston port rear pulley mod pics

This is so 2014..........

Re: Derbi variant piston port rear pulley mod pics

I was just a baby back then old man

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