Teramoto T-rev review

[Zaddict]

I stumbled upon this crankcase depression valve on Webike last winter and spent a few months researching it before taking the plunge and buying it. This is an amazing little piece of equipment.

https://japan.webike.net/products/21717465.html

Here's the review I posted on Webike:

Bought this for my 1990 Zephyr 550. I wasn't confident that it would have much of an effect, or that I would like whatever effect it did have, but after reading just about every T-rev review on Webike (almost all of which are four or five stars) and checking out some of the cool trev videos on YouTube, I took a chance. Result: I couldn't be happier. I'm not sure how best to describe the effect except to say that my bike rides much smoother now. It's more "civilized." Smoother idle, shifting and deceleration. Imagine you had a passenger and you were trying your best to make her ride as comfortable as possible. You'd be gentle with the shifting, maybe feathering the clutch to ease the transitions. That's what this feels like - a gentler ride without having to expend the mental energy of babying all the transitions. The best part is at highway speeds. Say you've got the throttle wide open. Normally when you release the throttle you'd feel a sharp deceleration. With this thing, the bike just keeps going smoothly. Less herky jerky stop-go. More flow.

Some fellow riders suggested just buying a cheap PCV or check valve instead. I don't think that would work. As I understand it, the T-rev consists of reed valves that open and close with each piston movement, thousands of times per minute. I don't think PCV valves operate on the same timescales - they're either open or closed (or maybe open a varying amount according to engine speed, but not opening and closing with each cycle).

There are a few downsides. For Zephyrs and GPZ's, this installs in the airbox, so it's a bit of pain to put in (have to remove the tank). And you can't see it, which is a shame because it's a nice looking piece of kit. I'm also wondering if it has a negative effect on airflow, though I haven't noticed any decline in performance (If anything, my bike seems more responsive). Another drawback is that these require maintenance - cleaning every 10K km and overhaul at 20K km ($50USD for an overhaul kit). And lastly, the price is ridiculous. That said, I think it's worth the money and am very happy with my purchase.

[Richard]

Nice that it works. I only wonder why, I mean there's always 2 pistons going down and 2 going up at the same time, shouldn't carter pressure stay the same???

[Zaddict]

There’s always a certain amount of blowby - air/fuel that leaks past the piston rings into the crankcase. Crankcase decompression for motorcycles is a pretty interesting and neglected topic. I’ll find some good links and post. Should have kept notes when i was doing my research.

I’m so happy with this part I’m considering buying some other unreasonably expensive but highly related webike parts - notably a performance ignition module.