Rz350 street bike. I added some k&n pod filters and some spec 2 pipes. Gave a small cleanup job on the intake ports, no highering or anything like that. Put in Boysen reeds. The main jet increased from a 280 to 320, which seems good. The bike would accelerate up until it matched rpm to throttle position and then it would almost four stroke (low throttle opening positions 1/8 to 1/4. I thought that richening up would help but the symptoms were lean. I went to a 30 from 20 on the idle jet and the symptoms were worse so I changed to a 15. The bike ran great when up to temperature but will not start from cold until it manages to get heat into itself from the constant kicking and occasional flutter. What do I do next? Needles are non adjustable and neither are the airscrews. Stock RZ carbs.
Are the enricheners/chokes working properly on both carbs? Are the slides closing all the way? I have never worked on RZ carbs but if they are like RD carbs you can mix up the slides and put them in backwards which seems to cause a variety of strange problems according to members at usa2strokers.
The slides are fine and are in the right way round. The choke is only on one carb and feeds across to the other one. I will check their function this evening. Jet lean for safety? There speaks a four stroke guy who once dabbled in the two strokes. I wonder why nobody has ever started a debate on four versus two
There really is no debate.. Just mention pie and Mr. lizard will be off on his favorite tangent .... It seems you have checked all the typical things that could be wrong I think you are WAY lean on the pilot jet.. possibly on the nozzle and needle also... Try pulling the choke and see if it likes that.. if so it is to lean... you can sort of modulate how much fuel the choke is releasing by carefully pulling the plunger off the seat..
Acquire some sort of adjustable needle. I would think they would be readily available from the aftermarket. I would put the stock airbox back on. You need to figure out what area of the throttle opening you are having the issues. Idle to 1/4. 1/4 to 3/4. 3/4 to wfo? Then you can figure out what area you need to mess with. You also need to make sure the floats are in good shape, set correctly and that the carb sync is as perfect as you can get it.
Where's the love Bob? In the words of the Great Mongo, lets chill. Come the the Nightmare at Nelson, I miss you.
The great who? "Pay no attention to the man behind the curtain" If you miss me take better aim next time I will let you exist in your own private nightmare...:up:
If it is any help, the toomey kits came with 410 and 420 MJ and used the stock pilots. The toomey airbox is just a RD350 intake boot with a pod filter on top.
When the RZs were modern there were shims available to fit under the needle clips to raise the needles and richen the mixture. You can try that. I also think that a richer pilot would help and that you may need to go to a richer needle jet. You have made enough changes to significantly challenge your induction system so it will take a little (?) effort to sort it our. Lyn Garland
Actually the US models came with non-adjustable needles as per most US spec bikes due to EPA regulations. The shims you mention may just be small washers that were supplied in most dynojet kits. http://www.toomey.com/html/intake_system_parts1.htm have the jet kit for $59.99
Ok, I have checked the carbs and everything looks fine. The #15 idle jets are not working so I will change them back to the #20. The mains are at 340 now and the top feels really good. I have the sudco book for the symptoms which says missed combustion cycles on a two stroke is too rich. When, after many kicks the bike fires it runs terrible at small throttle openings until it has warmed up and then runs well. I pulled the choke on when warm and the revs increased by 2000 at idle and you can actually leave the choke on but it does four stroke at small openings when the rpm matches the throttle opening. The same as with the choke off and the #20 in. I will try raising the needle. There is a small plastic washer underneath so I will see if I can get some shims to match and try again. It is unfortunate that it takes a while to get the carbs off to make the changes. Thanks everyone for your help so far.
Make sure you don't have an air leak at the manifolds. They get hard over time and can leak between the rubber manifold and the reed cage. A simple shot of gum cutter or contact cleaner around the manifolds while the bike is running will show a change in revs if they are leaking. Also notice the carb with the choke is the only one with a very small brass choke jet in the float bowl. It won't make a differance in running but it will make it a real bugger to start when cold.
Make sure you didn't swap float bowls. If there is only one choke with crossover, similar to RD's (and I think you mentioned this), Yamaha only drills the choke well on one carb. If you switch bowls, chokie no workie. <edit> Oops, just noticed above post mentions this already.
