I finally got the inspiration to get my RZ350 running properly. It's always been a very problematic bike to start when cold. I figured to start with a compression check but so far haven't found a target value for this bike. It's an '84 if that matters. Thanks in advance.
Don't know if it is true of the RZ, but the RD used a shared choke between the two carbs. Only one floatbowl had the full drillways and jet for the choke. If your switched the float bowls, it disabled the choke making it a PITA to start. Speaking from experience.
Correct me if I'm mistaken, but aren't you always fuckin' with this thing when it's 20˚ below outside? Can't you wait 'til Summer to have these same problems? At the least, throw a drop cloth over the bike and a 100w droplight under the bike for a couple days to warm it up a bit before messin' with it. Then see if the kickstart pushes through easily by hand. If you get enough resistance that you would be afraid to try to start it by hand, compression is not your problem. Prolly only gonna see about 70psi anyway...two stroke effective compression ratios are low due to the transfer ports eating up cylinder wall space, reducing the actual "closed" area where compression can take place. 6::1 is the factory compression ratio. Get a 2-stroke leakdown tester. I bet those old crank seals are breathin' all by themselves instead of holdin' their breath like they're supposed to...they should prolly be replaced as a matter of course anyway. If it ain't seals, you'll rule them out AND have a new tool in your shed.
10,300, only put 300 miles on it in the last 2 years. It's a barrel of monkeys for the first 100 miles, after that not so much...hard on the back.
Not good, not terrible but......4.9 compression ratio (ie 70 psi) on a cold engine...should be 6 to 1. Next I'll add a few drops of oil into the cylinder and see if that make a difference...typical trick for a 4 stroke, not really sure if it's appropriate for a 2 smoker. Started looking into a leak down rig ..what a giant PIA. I figure if I need to do a rebuild I might just as well replace all the seals too. Any recommendations for a 2 stroke shop within 100 miles of 17814?
FWIW RD/RZ use a labrynth seal in the crank center, so both cylinders have to be capped to do a leak down. Not that I would encourage you to do that. In about 10 years wrenching two strokes in the trade (including some truly beaten down ones off the res), I don't think I ever had a single "Ah-hah!" moment where I replaced seals and it miraculously made a bike start.
30+ years of RZs and never as I mean never, had a hard starting problem? The advice of the reveresed float bowls, you should look into...it's a common mistake made by many. The 84 CDIs were known to be much more problematic. If you do a basic rebuild, and you motor is reasonably stock ..you have a engine that should start effortlessly and be so reliable, you many never gave to rebuild it unless you race it? These motors are near bulletproof if maintained... but it's a 2 stroke... lol. Simple ..but ALL the components MUST be in perfect working order...they don't suffer ANY thing out of spec. If you are rebuilding it, new crank, full seals and clean carbs.... Should do the trick. If it's modified...then ? Who knows what..was it ported correctly, timing adjusted wrong, carbs too big... If yer close to Toomey...might be the way to go. He and his Brother know these engines like few others did.
Easily hands down the most fun motorcycle I have ever found in my life and I should have never will be another deliver such fun. I've ridden 80s bikes& 90s superbikes w w triple horsepower... Nothing is the sensation of speed during first few carries and delivers as many smiles as a wheel lofting rz350. True story...I got 6 blocks from the Yamaha dealer in 1985 when I got a ticket for doing a wheelie....lol Started off stock, then had Toomey pipes, Stage 2 porting , milled head, reeds ,carbs, shed about 25 lbs off the bike.... She smoked & was dirty n fast! She & I had more fun together...the best!!!! I'd love to buy a near stock RZ again...but prices are just too much these days... I have a total Franken RZ project now...nothing is RZ but part I'M the frame..the motor is stock but built 2 the hilt..should hit 75-80 h.p. depending upon my desired portworksince a RZ came stock with perhaps 50 h.p. on a Dyno...that's double the smiles.......
My first RZ ride almost scared the shit outta me in the first 1/4 mile. I was totally cool with 2-stroke dirt bikes and I owned an '86 GSX-R750 at the time, but taking a test ride on the RZ was something else. Couple hundred yards from Portsmouth Yamaha's parking lot, I was up near 80-ish(?) mph getting ready to peel off into a decel lane for a cloverleaf overpass. Rolled off the throttle and nothin'. Just short of completely blowin' the turn-in, a handful of brake did wonders. Holy shit did I learn something new that day. Followed up a couple years later on a Gamma, crossing a fourlane intersection with median from a red light. Thing smacked me in the face halfway through the intersection and proceeded to indicate about 70 mph on the other side. What a fucking hoot!
The Beeb comes through! I found the carb bowl on the choke side to have a small aluminum plug in the orifice that feeds the choke. The opposite bowl had no plug...just need to confirm that everything flows properly and I might as well clean everything anyways since I'm already here. I don't think I ever swapped the bowls as I'm pretty anal when into carbs, perhaps the previous owner did this...it was hard for him to start too.
Quite a few RZs were sold by disgruntled owners never could get their frustrating ours each ride and within hours miraculously they work perfect. RZs bought for pennies on the dollar.........darn those days are over
And the banshee people started looking for the engines. I still have a couple rz's in my garage that need a little TLC . I guess they will be my retirement project.
Any one here have some rz engine cases? I need a complete gearbox with cases, don't care about crank or top end.
