Looking for some advice. I just got my 1971 Rt-1 360 back from being bored and new piston installed. Also got new fuel lines, carb cleaned, new spark plug, etc. It fires right up everytime and low end seems ok, but mid range or just before powerband should come in, it has no more throttle or just kind of bogs out. I have gone through the carb multiple times making sure every jet and crevice is clean and blown out. I've changed the main jet to all different sizes and none seem to fix the issue. I haven't messed with the other jets. Please help! 

If you are changing the main jet and the carb is clean, then it may not be sucking in fuel. I would consider a pressure test, since it is new a static compression, look over reed valves. How about exhaust? Is it plugged up?

Do you have the blue powerband or the yellow powerband? 



Sorry, couldn't resist... seriously, not enough detail or facts at all to give you an answer.  My first thought is it might be running exactly as it should. 

Why?  Because in the few posts you have on here you asked about boring and pipes and that you heard the stock pipes are a power killer...  And you made ZERO comments about owning it for years and how it runs now compared to in the past.  So it sounds a lot like this is a new bike to you and it might not be running as you "expect"?  The RT1 is simply not a fire breathing monster.  They don't like to rev all that high and have a pretty smooth torquey mostly "midrange" power delivery in my experience.

Yeah, I know.  I made a ton of "assumptions" and I could be wrong on every single one.  But that's all anyone can do from your description of the "problem" so far.   More history, details on what has been done (have you checked the timing for example?), and/or a video (posted to YouTube and linked here) would be helpful.

If something is wrong, hope you get it figured out soon!

 

Power band & 360 don't realy go together--not realy as they pretty much grunt all the way without a hard hit.
In saying 'that', my modified 360 does hit hard because being too damn smart for my own good, i modified it way beyond what's good for it & its bloody awfull with little power then i'm hanging off the back.
So with yours the first thing i'd go for is va blocke exhaust way down the tail deep in tyhe non removeable spark arrestor.
I'd go there first.
If defo not that, then there's a very small Oring in the carb that seals the bowl that houses the side main jet & seals it onto the needle jet & if they don't seal the carb goes rich & limits it to about half throttle & to make things worse the blocked exhaust & 'that' carb problem react with in a very similar outcome.
Found a pic of the arrestor deep down in there. They have angled vanes & fill up with carbon & you wonder where the power went.
photos.app.goo.gl/RSPDtjWYpEeojfk66
Also here's an old short video of mine which i think in this case is just a standard 360 cylinder but with a clean exhaust, albeit a go fast exhaust, but mainly want show you how it revs clean with a clean system.

As Mark says, a video would be real good & we love video's & pics.
But videos with good audio help a lot in defining problems.
Longer video the better with taking the revs up to the limiting point assuming its less than what you'd expect it to rev out to.

Thanks, I will check those couple ideas. I will also have to try and get some videos. It seems fine at idle, and revs out smooth, but as soon I hop on, the mid/top range just falls on its face. My dad bought the bike new and it's been in our family since. According to my dad the bike has never had anything done to it. Ive owned the bike maybe 10 years. I got it running a few years back and planned to ride it more but that never happened and it's sat since then. This year I've decided to get it running again. I asked about bore in previous post because the bike had barely any compression at all so I knew it needed done. The guy that bored it for me said it looks like this will be the second bore (so maybe my dad doesn't remember it being done). I know the whole ignition system was gone through, but maybe I need to double check timing too.

Revving in neutral is completely diff. than when under load.


cliff

Thanks...
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It could just need to be ridden enough to get it good and warmed up too. 

In defence of your dads memory, it's possible the machine shop meant it will need to go up two sizes to clean up because Yamaha only go in 10 thou steps so if it had little compression then might've been very worn hence needing to go up 20 thou. Me just sticking up for the oldies haha. Keep up the good work saving these Old bikes.