Lack of top speed /coolant issue (RD 350 31k YPVS)

[mcslive]

Hello,
Ive tried a few places to get some advice for the problem i have with my rd 350 1983 31k but im now a bit stuck.
The bike goes through the gears and revs out in the lower gears but if you redline it from 1st you can get it to 160kmh and hold it for maybe 10 seconds before it "runs out of fuel". 
It loses power/surges and when I back off to 120kmh I can then do this yet again after a minute or two. Slowly revving out the engine from lower gears means I can keep the bike at 140kmh for a minute or two before the same symptoms happen.

There is also a coolant issue, it has pissed out and once before big puff of cloud came out from the coolant tank. 

I have looked into the float height etc. and it should be set OK. It has a set of aftermarket pipes but as mentioned it revs out lovely except when your going top speed zone.
Am I looking at potentially a rebuild? Previous owner tried to solve the coolant problem before but no luck it seems.

Any places to look into would be appreciated. Im not against a rebuild if it needs one but obviously id like to avoid it if I can.

Thanks.

[shaunthe2nd]

Could be lots of things, and I'm sure you will get some help.
I had something similar on my LC once and turned out to be a blocked vent in the fuel cap.
I ran it without a cap on the tank and it cured it so that's how I found out.

Good luck solving your problem.

[midlifecrisisrd]

Think the fuel and overheating are different issues

I'd say the head gasket is gone

Fuelling is either cap vent, vacuum tap or fuel valve in carbs

Steve

[midlifecrisisrd]

Oh and the aftermarket pipes, have you changed jetting to suit

What are the pipes?

Steve

[mcslive]

May 31, 2024 16:44:04 GMT 1 midlifecrisisrd said:

Oh and the aftermarket pipes, have you changed jetting to suit

What are the pipes?

Steve

From what ive seen they are czech pipes
I only bought the bike last august. I havent looked into if the correct jetting was put in, but from my understanding it should be ok as its power delivery is pretty much as I imagined except the top speed issue.

[mcslive]

374571139_10211319787666581_2585970749308068588_n by Niall McDonagh, on Flickr

Capture by Niall McDonagh, on Flickr

Added pic of pipes on bike and what im assuming are them.

[Yogi]

Just for info,your discs are on the wrong sides 🫣

[jon]

May 31, 2024 17:38:58 GMT 1 Yogi said:

Just for info,your discs are on the wrong sides 🫣

I can’t believe how common this is? Especially as the are stamped L and R from memory?

Jon

[jessy03]

May 31, 2024 17:15:58 GMT 1 mcslive said:

374571139_10211319787666581_2585970749308068588_n by Niall McDonagh, on Flickr

Capture by Niall McDonagh, on Flickr

Added pic of pipes on bike and what im assuming are them.

Your pipes don’t look like the lomas ones, yours do look quite short and narrow.

[LC_BOTT]

Was going to say the same thing, have you changed the silencers?

[mcslive]

Honestly I have no idea what the pipes geniunely are. I havent changed the pipes or silencers since I picked it up. I tried to find them online and from pictures it seemed to be as close to those I posted above. My guess is they are JL pipes without any badging on the silencers.

[midlifecrisisrd]

We're there not cheap pipes getting made somewhere similar on ebay for the last couple of years?

What is the ID of the stingers?

Steve

[andy748]

The balance pipe on the manifolds isn't pushed fully either. Andy.

[andy748]

Pushed fully home i mean.

[tacky1]

I would guess the head gasket is gone, I would pull the head and look there first, Only use a genuine yammy gasket as the aftermarket ones all seem to leak and you'll end up pulling the head again!!
Before tightening down the head loosen the cylinder base nuts a little and then torque the head down and then tighten the base nuts back up. The head torque is 20ft-lbs, i do mine to 22 and it seems to fix the problem.

I would also strip the carbs and get a verniers and check the float heights, They have to be near perfect, It sounds like its running out of fuel as if the floats are the wrong height......
Also, push down that balance pipe, you dont want air leaks as it will cause it to run lean and even seize it.......

[abar121]

Yep, the cooling issue sounds like the head gasket.

Athena ones are also very good. I've used plenty with no problems as have many others on here.

Once you have the head off, it's trivial to take out the bores / pistons. At the very least, get them measured and see if it needs a top end rebuild.

Ideally bottom end as well, but it's a start.

[stusco]

Good looking bike ,definitely head gasket for starters