70 R5 yearly check up (barney gets probed)

[m in sc]

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:





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. 



Thurs:


 

[RDnuTZ]

title reminded me I need to schedule that colonoscopy 

[Kawtriplefreak]

  

[soonerbillz]

Love it!

[irk_miller]

How often are you doing a leak down test?  I tend to do leak downs more than compression tests, since they give more information.

[m in sc]

never. have the kit, have really never found the need to do it. I know, sacrilege but.. 

[irk_miller]

never. have the kit, have really never found the need to do it. I know, sacrilege but.. 

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.

[m in sc]

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.