RZ/RD 350 & Misc. 2-Stroke Tech BBS

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PostPosted: Thu Jul 12, 2018 12:12 am 
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Greetings from Toronto, Canada! Incredible resource you have here!
I bought a 1983 RZ350 last summer. Have been researching, wrenching and riding (repeat to infinity!) and have an engine problem that I can't figure out:
When engine braking, whether downshifting or just rolling off the throttle, the engine pulses. Here's a sample - normal engine braking: waaaaaaaaaa, downshift, waaaaaaaa. Smooth, constant engine braking. My RZ: waaawaawaawaa, downshift, waaawaaawaawaaa. There's a definite pulsing. Not smooth at all. The pulsing stops when applying the slightest amount of throttle or pulling in the clutch.
Engine runs strong and smooth when throttle is applied thru all gears. Above 6,000 RPM, the pulsing is not noticeable.
Recent work done:
Professional shop 2x overbore, Wiseco piston kit.
New clutch plates - frictions, steels, springs but rubber rings are not installed. What are they for anyway?
Fresh gear oil.
Carbs synched visually: slides move together precisely, idle set with 1/16" drill bit under each slide.
New chain: old chain had very tight spots - maybe this bent the output shaft? No pulsing when accelerating, just smooth, classic, almost violent RZ power band!
I'm convinced I need to open the bottom end to find whatever is bent or otherwise not quite right.
Looking forward to the insights of the two-stroke collective.


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PostPosted: Thu Jul 12, 2018 6:12 pm 
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visual carb sync is ok, but the snail shaped suction velometer is better. I find small differences change the engine sound very easily. The devices were and are used to balance weber carbs VW's, etc. not expensive and very handy.

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PostPosted: Thu Jul 12, 2018 7:08 pm 
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Is this your first 2 stroke?

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PostPosted: Thu Jul 12, 2018 9:46 pm 
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They certainly make a different sound with no throttle applied. Not an issue I have heard of before and sounds odd if it idles properly as this is the same throttle condition. Your carb sync should be close enough to not cause a large issue. Likely some more information needed.


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PostPosted: Fri Jul 13, 2018 2:51 am 
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Location: Alberta, Canada
Like silverstrom said! (Hi John).

You are not supposed to engine brake with a two stroke, why? Because it's severely ineffective. It does not brake when you let off the throttle. Jam it down a couple of gears and you'll tranny brake, or break the tranny.
The 2 stroke engine is like an air pump. Ride it hard and learn to use the brakes if you need to slow down. There is nothing wrong with your bottom end.

Oh, welcome to the forum.

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PostPosted: Fri Jul 13, 2018 9:03 am 
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Ah crap I just wrote a long reply and left the computer before finishing and posting it - and lost the entire reply when I came back to post it and had to sign in again!!! Dang.
Point form this time:
- thanks for insights!
- yes first 2 stroke, many 4 strokes over the years. All sport bikes. I currently ride an 04 ZX6RR at Shannonville and Mosport track days. Track only. Got the RZ mainly for the street and the odd track day. Big mistake?
- I expected downshifting to be at least smooth. How do you know what gear to be in if you're not downshifting/engine braking while slowing?
- I am also experiencing stuck rings frequently due to premix, if I understand properly from my research on amount of oil VS RPM.
- premix is for racing only or leafblowers, chainsaws. Full throttle, short idle, full throttle, short idle. Mostly WOT. My 70cc mod BW scooter runs on about 32:1 premix with no complaints - the RZ not so.
- the autolube system adjusts the amount oil going into the cylinders very accurately based on RPM and throttle position - small amount at idle, large amount at WOT. That makes the autolube system the only truly dependable way to operate the engine whether its racing or street, to avoid over-oiling (and ring sticking) at low RPM and under-oiling (and seizure) at high RPM. Premix ratio is usually set for optimum lubrication at high RPM. A given tankful of premix is not adjustable like autolube system is. Can you run a premix with less oil for street use to avoid stuck rings? 40:1? 50:1? The constant danger would be seizure from prolonged WOT throttle but on city streets WOT is rare...? Autolube is the only sane answer.
- I'm fairly sure my autolube pump should be overhauled to make sure such a critical part is working properly. Anybody know where I can get this done in Toronto Canada or elsewhere? I have seen the name Arrow more than once while researching.
- I went into the garage last night and looked my RZ straight in the headlight and said in a low, dangerous tone: " Smarten the h*ll up or you will be sold real cheap on Kijiji. I am this close." Of course I didn't mean a word I spoke.


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PostPosted: Fri Jul 13, 2018 10:25 am 
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All is forgiven. It seems that my stern warning last night worked!
On my way into ripping off the top end AGAIN expecting to find the rings glued to my new Wisecos, I removed the carbs and took off the float bowls for an inspection (yes I have done this too many times to count over the past year!) - the left pilot jet was clogged with a ball of fluff that I swear had long ears, whiskers and a fuzzy tail! It responded to the question: "Peter?". That certainly explains the pulsing at idle, and I DO have an inline fuel filter!! I re-assembled with fingers crossed the entire time and she started and responded to the throttle very crisply with a quick pump of the starter. Hmmm. I don't believe it. Test ride. O M G! Crisp throttle response, minimal stuttering from idle to 1/4 throttle (I'll tweak the air screws) and guess what? Absolutely smooth as silk when rolling off the throttle and engine braking. SILK. Waaaaaaaa, downshift, waaaaaaa. Beautiful. Now I'll park it in my living room because I don't dare ride it again for fear of screwing it up!! She runs better than ever. Classic RZ two stroke music coming from the pipes. This is why we love 2 strokes.
My points about how critical it is to use the autolube system at all times for all modes of operation vs premix is still up for discussion. I'd like to hear what the veterans in the collective have to say. I am officially looking for someone to overhaul my pump.
Thanks again for the feedback, folks!


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PostPosted: Fri Jul 13, 2018 10:30 am 
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the pulsing is not normal. I have felt this before on a bike I had very briefly. I believe its a lean condition in the pilot circuit (plugged?). someone correct me if I am wrong.

EDIT - posted as you posted last.

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PostPosted: Fri Jul 13, 2018 2:07 pm 
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Send your pump to arrow in the uk for a service.(cheap insurance)
are you running the pump and sometimes pre-mixing ?
mark

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350LC,Athena 392 big bore,stock porting,swiss cheese air box,stock reeds,spec11 pipes.(now TSA big bore pipes)
She might not be pretty but she will always be a fun ride


1982 YAMA RD350LC
2004 BMW R1150RT
1989 FZR1000
1994 FZR1000


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PostPosted: Fri Jul 13, 2018 3:04 pm 
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Dont pre-mix if you are running with the oil pump. You will be filling your motor with 2-stroke oil. Rory hates this!


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PostPosted: Fri Jul 13, 2018 4:40 pm 
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Nokturnal: right on, plugged pilot jet!
Two-stroke-brit, and evan_calgary: thanks for the Arrow tip. I removed the autolube plumbing and have been running approx 32:1 premix (yamalube) since I bought it, then realized recently thru researching that the autolube system should be used for optimum lubrication not to mention a big reduction in oil consumption. I put the plumbing and throttle cable back on, set to Yamaha service manual specs (straight gas in the gas tank) and the left carb was spitting out oil. Not sure if the oil orifice in the carb is plugged causing it to squirt out of the hose at the carb or if something else is going on so I took out the oil reservoir, pulled the plumbing and cable and went back to premix. The pump has been in its place the whole time, I just drained the oil and removed the plumbing/throttle cable. Probably not good for the pump to run dry...I was at the Yamaha dealer today and new autolube pumps are still available. I might just buy it and be done. Sending my pump to the UK for an overhaul will probably cost more than the $350 for the new one from Yamaha. I'll send Arrow a message to find out cost. Thanks!


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PostPosted: Fri Jul 13, 2018 4:49 pm 
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One more point to Evan_Calgary's comment: When I had the cylinders off recently for the rebore and new cylinders, I noticed that when I rotated the crankshaft, there was definitely oil on the circular crankshaft components on each side of the connecting rods. Wiped it off, rotated the crankshaft, more oil. I tried to look into the bottom of the crankcase to see just how much oil was sitting down there but couldn't get a good look. The oil is a greenish colour, the same as was in the oil reservoir when I first bought the bike last summer. I think the autolube system was malfunctioning long before I owned the bike. Will this oil in the bottom of the crankcase eventually burn off? I certainly don't have to worry too much about dry main bearings!


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PostPosted: Sat Jul 14, 2018 4:31 am 
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Premix 50:1 with a high grade race quality oil. You save weight with no oil tank, oil pump. Gain a modecum of hp with out pump drag. Track bike application. I'll know more when I start tracking mine.

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PostPosted: Thu Aug 09, 2018 3:33 am 
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One issue with the oil pump is the check valves get full of crap over the years and stop "checking" the flow of oil. The oil tank is mounted higher than the carbs. Thus, when the engine is not running, there is a slow drip-drip of oil into the carbs, which then trickles down into the cylinders and eventually can make its way into the bottom end. This would explain several of your symptoms.

Get the oil pump serviced by Arrow.

I wouldn't worry about any fugitive oil in the bottom end. It should get picked up by the air/fuel flowing through the cases and eventually get burnt off. A bit of extra lubrication in the crank cases isn't going to hurt anything.

IF you are gonna run without the oil injection system, make sure to plug the oil inlets into the carbs as they could allow excess air to be pulled into the engine and result in lean running.

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'82 RD350LC in '81 colours - Built by "Solo 2" OEM pipes, UNI filters
'90 RZ350F2 with 31K motor, OEM F2 pipes & airbox


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PostPosted: Thu Aug 09, 2018 2:29 pm 
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and remove the pump or it will wear out in quick fashion without the lube .
mark

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350LC,Athena 392 big bore,stock porting,swiss cheese air box,stock reeds,spec11 pipes.(now TSA big bore pipes)
She might not be pretty but she will always be a fun ride


1982 YAMA RD350LC
2004 BMW R1150RT
1989 FZR1000
1994 FZR1000


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