I liek to check compression on occasion, and figured it was time to check barney. Mind you, as -far as i know- its a bone stock topend, but it def has been off before. Ive had this bike since 2012 or so, and its always mechanically ran oddly well. It does have a bit of noise at cold startup, im suspecting a crank bearing is wearing, but its been doing it for 8 years.
I did change the crank seals years ago, but have never, i mean never, even had a head off. Heres why:
(https://2strokeworld.net/wp-content/uploads/70-R5/2025/70r5_pistons_1.jpg)
(https://2strokeworld.net/wp-content/uploads/70-R5/2025/70r5_pistons_2.jpg)
and, if it shows, a video w a bore scope. To be honest, i wasnt sue what pistons it even had in it.. look to be cast, and i cant see an overbore mark but not sure.
https://2strokeworld.net/wp-content/uploads/70-R5/2025/70-r5-rhc.mp4
https://2strokeworld.net/wp-content/uploads/70-R5/2025/70-r5-lhc-cleaned-dome.mp4
the left cyl, i did use a dremel with a brush attachment and clean the center of the piston, so that bright spot was intentional.
the bore scope is a cheap klein tools one that just plugs into my phone, for like 40 bucks it does really well. (and fits in the plug hole).
So, its good, technically.
BUT, i want to freshen up the crank since.. it may be 55 years old now. also, take the opportunity to swap in a 6 speed ( i have all the stuff to do it a few times over)
This will also give the opportunity to vapor blast the cases and paint the cyls correctly, etc.
:toot:
Thurs:
(https://2strokeworld.net/wp-content/uploads/70-R5/2025/20250117_173503.jpg)
title reminded me I need to schedule that colonoscopy :eek:
:metal: :metal:
Love it!
How often are you doing a leak down test? I tend to do leak downs more than compression tests, since they give more information.
never. have the kit, have really never found the need to do it. I know, sacrilege but.. :burnout:
Quote from: m in sc on January 21, 2025, 10:20:07 AMnever. have the kit, have really never found the need to do it. I know, sacrilege but.. :burnout:
No judgement from me. I was more curious. I was taught by my old man to always do them even on SBCs or VW boxers when I'm looking to buy or just bought. I have some friends that have melted plenty of pistons and they've made me paranoid about sucking air. I hope I'm a little better mechanically and their troubles are more about them. Every time I've checked my hybrid RD, the leak down was the same, so I figure I could chill out a bit.
i check crank seals when i get a bike, usually change them. pretty easy to see if they are leaking on a twin yamaha... if they are hard, i just change them. Any time i ever really did it was on kawi triples and i don't have any more of those.