So I was cleaning up my barrels and don't know how I missed this. One barrel looks like it was ported on the sleeve. Can someone tell me what's going on here? Not sure how I missed this, and why the heck one barrel is done and not the other. This basket case is sure proving to be a mystery, but I'm learning quite a bit.
Thanks.
Hmm
Strange, guessing whoever did it built 2 engines up at the same time.
Knife edging isn't something you see done much anymore, saw some photos of the last GP bikes ports & the dividers were quite thick & rounded instead of sharp
What are your plans, 2 cylinders the same or close your eyes & reassemble?
With all the work going into it I'd rather not close my eyes. I'm still learning. If knife edging is a no go it looks like I'm in the market for a set of barrels, or at least a replacement of one. I was close to sending them over to chuck to get a port job done as I knew they had been messed with, just didn't know how I missed this, and what the ramifications of it were. The left side case had looked like it got much hotter than the right side upon disassembly. The larger barrel on the crank looked like it got hot. Probably should start a build thread so I can keep track of things. All things considered I'm excited to be able to learn. I'm sure this is just the first RD400 I build.
Just thinking out loud, the guy I bought the bike from seemed to throw this bike together. Everything on it was beat, it looked put together, but nothing was put together. . Cheap is still cheap so I'm assuming he replaced a barrel but didn't have knowledge like me.
I'll do a bit of research, but if anyone can shed light to educate me I'd appreciate it.
Easily fixable...
No big deal to address and match both cylinders.
I've seen way worse.
Yes, knifing the transfers are old school porting like Tony said.
It's usually other areas I'm worried about like port heights, deck heights, bore sizes, etc.
Chuck
I will have them finished like this when I'm done. (Paul's 62HP build)
(https://photos.imageevent.com/supertune/paulsrd400/large/20180824_211852.jpg)
Don't panic, the knife edge can be made good.
The idea behind that mod is to get air flowing in the main transfers before it starts to flow from the auxiliaries. Both sides on both barrels should be the same. I don't know anyone who has tested sets machined to different amounts of cutaway to measure the effect. What I'd do is to get all 4 at the same height and straight across - but just on the main transfers. Do not machine/port the small ports. Cut them as flat as possible and then just round off the lower edge to improve gas flow.
That won't make a whole lot of difference to power, but will look trick and both sides will be balanced.
As Chuck mentioned, height width and angles of the transfer port outlets are way more important to power and how the bike runs.
I highly recommend sending them to Chuck to get them matched. You will be pleased and confident with the result, no doubt.
Two issues and possibly a third 1) Whenever I do a set of cylinders that have been knife edged on the divider between the two transfers I take the time to round them. Jan Thiel did an amazing amount of incremental testing at aprilia with AMAZING RESULTS and that's pretty much why 99% of tuners now days use rounded dividers between the transfers and rounded entries at the sleeve because of a lot of things a lot of people learned from his work (and many other world class tuners of course). Tom Turner used to tell me the same thing. 2)and a different issue is the height of the sleeve cut at the base of the transfers, TT and other tuners agreed way back when with what Yamaha also saw at the time which was that raising the area at the base of the main transfers helped but going all the way across saw a negative effect and it's because the auxillary transfers just seem to really benefit from the extra auxillary port length in these bikes. 3)and lastly If they knife edged the base of the transfers on the one cyl make sure they didn't do anything else, inexperienced tuners would sometimes just knife edge the transfers and raise the ex and call it a port job lol... Just like chuck said we have to work around what other people have done in the ports all the time, were used to it.. Ed
So can a knife edge be built back up with epoxy (after a thorough cleaning, or course)?
Rob
It's not necessary. Just round it off to take the sharp edge away. Try not to take too much metal off.
How much power loss is taken from porting down to open it up. For instance on the barrels I posted. I've seen from my research on different 2 strokes a simple rounding off with the caution of not opening it up. I know I'll be compromising with these barrels, but it may effect how much I do to them in the long run.
Realistically, my bike will be a tool around town bike, not a mint example anyway. First one is to learn, so I am. . .
I think Jspooner quote applies here...
"Just quit brain fucking it and get it done"
Time to move on to things that make real power like ordering your Spec 2 F1's and some TM34's to use some VF reeds.
If you don't put air through the pump, no power...
Chuck
Maybe I was confusing when I said don't take too much metal off. I didn't mean to scare you.
Let's try to be clearer. Machine both main ports down on both barrels to say 7mm below deck. Do NOT machine down the auxiliary ports. Just that mains - like that one barrel.
Then on the bridge between the two transfer ports, just round off the top (when it's upside down). Perfection is overrated. Slightly rounded off is fine. The motor can't tell if it's a perfect radius or just slightly less pointy, so go for it.
Ty to radius the transition from the new lower (higher) edge to let the gas get around the corner and up the transfers. getting the bottom of teh transfers perfect is a lot less important than matching the outlets.
A slight mismatch at the bottom won't be noticeable on an old street motor. Just do it.
Quote from: teazer on June 25, 2019, 11:46:41 PM
Maybe I was confusing when I said don't take too much metal off. I didn't mean to scare you.
Let's try to be clearer. Machine both main ports down on both barrels to say 7mm below deck. Do NOT machine down the auxiliary ports. Just that mains - like that one barrel.
Then on the bridge between the two transfer ports, just round off the top (when it's upside down). Perfection is overrated. Slightly rounded off is fine. The motor can't tell if it's a perfect radius or just slightly less pointy, so go for it.
Ty to radius the transition from the new lower (higher) edge to let the gas get around the corner and up the transfers. getting the bottom of teh transfers perfect is a lot less important than matching the outlets.
A slight mismatch at the bottom won't be noticeable on an old street motor. Just do it.
Right on...Thanks Teazer for the reply.
6mm was what I normally do. I have done as much as 10mm with not much difference after 6-7mm.
Chuck
Quote from: SUPERTUNE on June 25, 2019, 10:21:24 PM
I think Jspooner quote applies here...
"Just quit brain fucking it and get it done"
Time to move on to things that make real power like ordering your Spec 2 F1's and some TM34's to use some VF reeds.
If you don't put air through the pump, no power...
Chuck
:clap:
More learning than overthinking. I'm going as fast as money will take me. . .lol