rz350 engine not running right, help

[stockxr]

Yeah it's not a banshee but it's close. I pulled my 85 rz350nc(9993 miles on the clock) out of storage and cannot get it to run right. This thing ran great a few years ago. It bogged and died on me within a 1/4 mile and would not restart. It is all stock except for possibly the reeds. Are the stock reeds metal? The bike starts on the first kick with the choke on when cold. It idles at 1200-1500 rpm for about a minute then the idle lowers a little like it wants the choke off. That seems normal to me. It all goes wrong when I turn the choke off. It seems to idle just fine for 15-30 seconds then the idle starts to creep up to 2000-3000 rpm. Also it does not rev out very clean. When I whack the throttle wide open it gets to around 9000 rpm, then cuts out and continues at 9000 rpm.

 

It sounds lean. Maybe starving for fuel, or has an air leak. This is what I have done so far:

 

new plugs(br8es)

cleaned the air filter and checked the air box

cleaned the carbs(twice)

checked the float height(good)

no gas in the floats

checked the float bowl fuel level while running the engine(good)

pilot screw is 1-1/2 turns out

cleaned the fuel tank(found some particles)

installed a fuel filter

ran the bike with the gas cap and vent lines off(no change)

replaced the carb joints(the originals were cracked,no change)

replaced the reed block gasket(reeds are good, no change)

 

If someone with banshee or rz knowledge could respond I would be grateful. I have worked on my own two stoke dirt bikes, so I am not a complete newb. This bike has me stumped.

 

Thanks in advance,

Chris

[2/2 many banshees]

sounds like a fuel problem check and clean the carbs.

[LS1Inferno]

sounds like a fuel problem check and clean the carbs.

 

said he did it twice. strange i dont know alot about the bikes but they have PVs right? they could be gummed up. and metal reeds? also check for the choke tube between the carbs

[Wildcardracing]

When you cleaned your tank, did you inspect and clean the petcock real well??. My honest suspision is that you're crank seals have dried out on you while it was in storage and you now have an air leak. Sitting and not being used is in many cases the hardest thing on an engine.

[stockxr]

said he did it twice. strange i dont know alot about the bikes but they have PVs right? they could be gummed up. and metal reeds? also check for the choke tube between the carbs

 

The PV is working and adjusted properly. It self cleans when you turn the key on and opens around the right rpm. Choke tube is installed. I have the bike put together right and everything adjusted. The fuel appears to be flowing good. It will flow about 12oz in around 25 seconds. I also inspected the fuel level in the float bowls will the bike is running and its right.

 

I hope it's not the crank seals. It is an old ass bike(23). Could that cause and air leak symptom like this?

Edited July 6, 2008 by stockxr

[2/2 many banshees]

When you cleaned your tank, did you inspect and clean the petcock real well??. My honest suspision is that you're crank seals have dried out on you while it was in storage and you now have an air leak. Sitting and not being used is in many cases the hardest thing on an engine.

I didn't think of that slobanshee06 good point maybe a air leak some where

[Wildcardracing]

If it has an air leak it will act like it's lean because it is lean. I'd have a leak down test done to be certain it's good. It should hold 6psi in the crankcase for 6 minutes. Also, did you look at your pilot jets real well? you should be able to see a little bit of light through them, they can be a !@#$ to get clean after sitting for any length of time. My honest bet is an air leak though.

[stockxr]

If it has an air leak it will act like it's lean because it is lean. I'd have a leak down test done to be certain it's good. It should hold 6psi in the crankcase for 6 minutes. Also, did you look at your pilot jets real well? you should be able to see a little bit of light through them, they can be a !@#$ to get clean after sitting for any length of time. My honest bet is an air leak though.

 

Your right about the pilot lets. Even after putting the bike away dry they were still clogged. I cleaned the pilot and main jets with cleaner, a guitar string, and compressed air. I also cleaned the float bowl and carb body with a sonicare tooth brush. That thing worked bitchin!

 

What's involved in performing a leak down test? I have never had to do one. Is there anything electrical that could cause this? Coil or CDI? The lights act normal. They don't go to full bright until 2-3K rpm like they should and there's no flickering of any kind. The battery is good and the charging system works.

[Wildcardracing]

Your right about the pilot lets. Even after putting the bike away dry they were still clogged. I cleaned the pilot and main jets with cleaner, a guitar string, and compressed air. I also cleaned the float bowl and carb body with a sonicare tooth brush. That thing worked bitchin!

 

What's involved in performing a leak down test? I have never had to do one. Is there anything electrical that could cause this? Coil or CDI? The lights act normal. They don't go to full bright until 2-3K rpm like they should and there's no flickering of any kind. The battery is good and the charging system works.

The easiest but unfortunately most expensive way would be to have a shop do it. You will need two expansion plugs for the exhaust(pipe removed), a compression guage(with removable schrader valve) or pressure guage and two plugs with a schrader valve to clamp in your intake boots. You will pressurize the crankcase to 6psi and watch the clock. It should hold for 6min. If it doesn't you can use soapy water all around your gaskets and seals to find the leak. Hope that helps.

[stockxr]

Can you buy the exhaust and intake plugs or do half to make them?

[Wildcardracing]

I made my own, but you might check tdr (tony doukas racing) F.A.S.T. and mmatv. Some of these places may have a kit...not sure. Someone else may chime in here with a good place to buy an entire kit. I just used some rubber expansion plugs for the exhause side and welded caps with valves in them on some tubing for the intake side. Then I just use my compression guage with the schrader valve removed in the spark plug holes, works quite well.

[BenBB]

I agree with slo I would suspect an air leak on the LH crank seal, especially since the carb boots were cracked, anything rubber that's not submerged in oil is a potential problem. I'm pretty sure the stock reeds were fiberglass with metal stops like Banshees', not 100% there tho, just what was in my RZ motor when I got it but there's a good chance they got swapped somewhere before I got ahold of it. Anyway if you don't already have a means of doing a leakdown test you can always try the can 'o ether method, with it idling spray here and there with the ether and listen for the RPM to increase, in this case with the choke on...if you're REAL careful you could try to hit that crank seal behind the flywheel while she's spinnin'. Good luck.

[stockxr]

Could the carb being out of sync cause these symptoms? Just a shoot in the dark.