My 4,000 mile '75 350 has 95lb compression. It runs starts and runs good but will occasionally foul a plug during warm up. Once warmed up, it has never fouled one. I have the heads off and it is still stock bore and the cylinders look okay. There were no rattles or noise inside when running so I don't think the piston top cylinder gap is excessive. I will pull the cylinders tomorrow for a more in depth look and measurements, but right now I am thinking of knocking the glaze off the cylinders and installing new rings. I have spare cylinders and heads that I may send off to be modded but for now a re-ring job may be the ticket.
Who has std bore rings that will fit the Yamaha pistons. Yamaha apparently doesn't.
Thanks again for the advise! I don't know what I would do without it.
:thumbs:
if you have std rings (not dykes or 'l' shaped) here you go: https://yambits.co.uk/rd350-piston-ring-kit-std-p-8353.html
Again, thank you. I will pull the cylinders tomorrow and determine the style of rings.
:thumbs:
I might have some stds. in my stash. Let me know what style.
Well, well, well; Pulled the cylinders today. Things looked great. Piston to cylinder was good, no scratches in the cylinders, nor were there any scuffs on the pistons. The rings were the only thing out of spec at .022. It is still standard bore. Everything cleaned up good and was just wanting to bust the cylinder glaze and put in new rings. BUT! They are Dykes. Looks like there aren't any out there. Unless someone knows of some. I have filed down 1st oversize rings to std bores many times on 4 strokes, but I don't know about doing that with these, so I am not looking for 1st over.
Ebay has Chinese Kveldwulf piston kits for $45 which they say are standard. Anybody know if they are any good?
Any other suggestions? Please..............
IF i were in your position and going to swap JUST pistons, I'd buy the yambits std pistons. I run them in my tzr250. (1st over in mine) https://yambits.co.uk/rd350-piston-kit-std-p-8146.html
me? id just freshen it up to a .25 over bore to make sure its all square and nice.
Following your advise, I just ordered the .50 over simply because they were cheaper along with a couple of other items.
:thumbs:
Std bore dykes rings are out there, they're just a little on the expensive side.
Yam part # 360-11610-02
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p4432023.m570.l1312&_nkw=yamaha+360-11610-02&_sacat=0
https://www.cmsnl.com/products/piston-ring-set-std_3601161002/
If the pistons and bores are still good you would come out ahead just buying 2 sets of OE std dykes rings instead of paying for 2 new piston kits and 2 holes bored, and you would preserve two oversizes in your cylinders. Also when buying any vintage OE rings I would ask the seller to confirm the ring style to ensure they are "L" (dykes) type because I've seen many mislabeled on eBay. :twocents:
You make some good points and being that my cylinders measured good, I would have preferred to just go with new rings. BUT, these lasted 49 years and 4,000 miles. And although it was time to change, they weren't junk and I could have ran them longer.
I will never put another 4,000 miles on the bike. I just don't ride that much any more. And there are a ton more oversizes available. So, this is the most practical way to go. Unless I foul something up, this will last a lot of years. Who knows, maybe another 49. :thumbs:
I didn't see any std 350 rings in my stash, however I will be posting a list of what I do have soon. There is at least 20 sets in my box.
20 sets!! Good God!! LOL
fwiw you can file dykes rings 'down to size' have done it years ago. :twocents:
Many years ago, I did a lot of work on 3 wheelers. In particular the Hondas. The Big Reds back then were very prone to burning oil and lots of guys wanted their 185cc rides kitted up to 205cc. I did dozens and dozens. Some guys wanted Honda parts rather than Helm or whoever. But the Honda rings came out of the box out of spec. The end gaps were HUGE. And that was the problem with the Big Reds burning oil. For the guys that wanted Honda parts, I would get the next size rings and file them to spec. Given Honda's reputation for quality, I never understood that.
But I had never tried filing Dykes. Never really had the need. If I could have found .25 O/S Dykes for my 350, with your input, I may have tried it. But..................
Does this bike still have its original crank seals?
I cannot know for sure, but I would think so.
I stopped by our local speed shop to ask if they can bore my cylinders. He can't bore cylinder bores that small, but can rigid hone them to size since it is only 2 and not that much oversize.
But he brought up a good point that I didn't know and would have liked to explore had I known. There are ring makers that can make just about any ring. In fact there are several ring makers that can do it. I don't have any idea what the cost would be, I just thought I would pass this along as an FYI.
Just some advice from an old timer. Take your cylinders to someone that can measure them and see what condition they are in and proceed from there.
I agree. my local guy is 80 bucks a hole and does a fantastic job boring cyls, bern doing mi e for over 20 yrs.
Good advice.
The speed shop is a full-on race shop. They rebuild big dollar stuff of all stripes for the nostalgia racers. Mostly muscle cars. They maintain and deliver on call over a dozen race cars to races. They are leaving next week for Florida with several cars for the first race of the season. My cylinders are really small potatoes and do not have to be as precision as most of their customers. The ONLY reason he will mess with them is because we are personal friends and I do him some favors with my tractor. My cylinders are in good hands. That I am sure of. :thumbs:
Now that was FAST!
I ordered my parts from Yambits over the weekend and they arrived this (Thursday) morning. 4 days from the UK to Illinois. Heck, I order stuff from either coast here in the U.S. and it takes that long or longer.
I really appreciate the heads-up on Yambits. I was not familiar with them at all. :thumbs:
4 stroke and 2 stoke boring is different. make sure he chamfers the ports correctly if he has little or no 2 stroke experience.
That will probably fall to me. It's been a long time, but I have done it before.
Quote from: m in sc on January 02, 2025, 10:59:39 PM4 stroke and 2 stoke boring is different. make sure he chamfers the ports correctly if he has little or no 2 stroke experience.
Do you personally use porting tool of some type- or by hand?
I use a tootsie roll sanding drum, small for porting. long arbor, on a die grinder . more a setup for porting automotive heads but works well for this. the arbor is about 6" long