RGV250 Carburation Problem? Where to start?

Hey Folks,

I am hoping that someone can point me in the right direction. I recently acquired an 1990 Suzi RGV250. I always wanted a two stroker street machine and thought that I found a good one. It turns out that the carbs are a too large (maybe) as the stockers were 32mm keihins and then ones on this are 34mm with 230 mains.

Anyway, the seller represented this as having a flat spot midrange, but I cannot get it to even move under its own power. It will idle, but immediately stalls if given any throttle. I am a two stroke neophyte and am trying to figure out where to start. It could be an ignition problem, carb problem, vacuum leak,. etc.


I was thinking about dropping the main jets to 190 or 200 and working up from there. In general, am I starting in the right place?

Thank you !
Tom

 

First, take the carb apart and see if it's dirty, gummed up from rotten gas or has loose parts in the bottom of the bowl.
The main jet has minimal effect right off idle so if it won't drive away from a dead stop, check fuel delivery from the tank, float level, pilot circut for clogs and pilot screw position.
Next look at needle selection and position.
Going lean on a main jet if you don't have any idea of a base line can result in crispy piston syndrome...

 

if the bike has been sitting .. carbs are prob gummed up..
clean the carbs ! first.. make sure all the ports in the carb body are clear... try that first...
good to see someone still loves two-strokes

 

Be sure to remove and thoroughly clean the main jets, the pilot jets, and the emulsion tubes. Make sure that the needle is not varnished and also check the needle and seat to make sure that it is working well.

Start at a jet that you KNOW is rich and work your way down. Put the needle in the middle to start with.

Once you find the correct main jet, move the needle based on the throttle response. Moving the clip up makes it leaner, moving it down makes it richer.

Valves are for toilets

 

REEDS. Other than gummed up carbs, the next thing to check is the reeds to see if they are cracked or broken.

parillaguy

 

You drop to a 190 or 230 and you will be buying a new top end brother!!!


If you have the 1990 rgv250 L export model, stock carbs are 34mm with stock jetting at 270/280, if you have pipes on it, you should be at 260/270.

First time running/riding the bike?

A quick to do list:

Use new good fuel
Clean, inspect Sync/adjust PV's
Clean carbs and jet properly (dont trust what PO told you)

If the flat spot remains, it may be an SAPC issue which is easily fixed, but definitely start with the carbs!!!!

Pete

 

RGV

34s should be the stock size carb. (unless it is a japan only restricted model) You should have the air box on as well. Make sure there is a good seal at airbox to carb boot. The right carb (to the lower cylinder) runs richer pilot and main than the upper cylinder carb. The pilots are notorious for getting clogged. If the bike idles, try starting off with the choke engaged to make it rich and see if it still boggs. Stock jetting should be fine with the air box on. There is very little power to be had on these bikes by trying to run (and jet) with open carbs or pods.

RGV and aprilia also run pilot and main solenoids that electronically add air/fuel at different revs. If someone has removed them make sure the port on the carb is blocked off or it will suck air. There are 2 ports for each carb. They are white (the black ports are vent and fuel overspill drains and should not be blocked).

Best forum for info is: http://www.rgv250.co.uk/

 

THANKS!

Thanks for taking the time to help me folks!


I pulled the carbs and there is some gum in the bowls, so I will make sure everything gets a thorough cleaning. I now have serious doubts about all of the PO's "maintenance". He also said that he "inspected, cleaned, and adjusted" the power valves. I will make sure that I check those before I attempt a re-start.


I am still not exactly sure what I have. (I guess I need to look up the ECU part number as well). Is there a serial number reference that anyone knows of offhand?


As for the carbs, there are definitely 230 mains in each. What is also really screwy is that there are .6 and 1.1 pilot jets in BOTH carbs. So, I assume that I should put the 1.1s in the lower carb?


My plan was to:

1. Thoroughly clean, clean, and clean the carbs and jets.
2. Make sure that there are no leaks in the lines or plugs on the carbs (there are no servos)
3. Make sure that there are no leaks in the carb boots at the head or at the carb. I guess I should also check the balance/boost tubes.
4. Inspect the powervalves.


There are aftermarket pipes on it. Do you think that there is any danger of going too lean if running the 230 mains while I sort this all out?


THANKS AGAIN FOLKS! I will let you know how it goes.


I cannot wait to get my much needed 2 stroke fix!!!!!!!


Regards!
Tom

 

>>http://www.rgv250.co.uk/<<

WOW, Great site. Thanks for the link!!!

 

Tom, start with the 260/270 combo and work either up our down.

Pete

 

My 1992 model had 34mm carbs stock. Steve Biganski recommended me putting on 38mm carbs if I could fit them. Of course I had Kit ignition, Jolly Moto pipes installed too..

 

No wonder it ran like sh*t Chuck, kit SAPC with Jolly's????:tut:

You would have grabbed first place it you had the full Monty!!!

Kit ignition needs all the other kit bits to work right..., still you shouldnt have sold it



Pete

ps, digging the new avatar

 

Like others said, make sure everything is clean and to spec.

But, I had the exact same issue you are describing on my TZR250. The idle was great but it would fall on its face and you couldn't get away from a stop. It has Mikuni 34's...not sure if that is the same as yours. I found the carbs on this are EXTREMELY sensitive to mixture screw setting. I (and several others) chased this for days. On a whim, I turned the mixture screws a half turn and it now pulls away from a stop like a champ. I've never seen a bike so sensitive to this.

Oh yeah, the problem started when I cleaned the carbs, didn't check the mixture screw setting and "just backed the mixture screws out 2 turns as a starting point".

 

I didnt, I traded Tim Morrica for a 125...Then he sold

I think there were some more trick bits from Padjets but I cant remember, 17 years ago

It ran good enough to bring me from the 3rd wave in D-Super to a podium everytime I raced it in 95. Well except for the GNF where I went off under the bridge but never crashed....

 

As said, check the pilot jet/air screw passages, it only takes a *tiny* piece of crud to plug that tiny microscopic size pilot jet hole and make a bike fall on it's face.

 

The holes in the pilot jets are VERY small. Hold them up to the light after cleaning them and make sure you can see through it.

 

Ahhhhhh it's Fooked!! Sell it to me!!

 

Air jet position?

I am going to give the carbs a thorough cleaning tomorrow and try again.

I am a little confused on the air jets and cannot figure out which should be in which position. Is the right or left port the main? I have .6 and 1.1 jets. I assume that the .6 is the main air jet? again, which port does this go to (left or right)?


I think that one of the POs slapped these carbs together. In the lower carb, there were two 1.1 air jets, and in the upper carb there were two .6 air jets.


It will be a great day if I can get it running after they are cleaned up.
Can't wait to get this bad boy ripping.


Thanks again for all of the suggestions folks. even the one that says it is f'd and to sell it. that will be the last resort ;-)

 

Electrical gremlins?

Well the saga continues.

I cleaned all of the gum out of the carbs, ports, jets, etc. and have the air jets in the right place.


I can get it to pull to redline erratically. It will get to redline, bog down, stall and then sometime run OK. It idles like a swiss watch everytime on a restart. Same thing happens with choke on or off.


I started to think that I may have an ignition problem? I checked the coils and I get 6.0 K Ohm and .3 ohm on both. HOWEVER, I discovered that one of the plug caps is a resistor cap (6K ohm). I am wondering if this is causing the CDI to go crazy?


My next step is going to be to get some new ignition cables and with non-resistor caps.

Are those resistance settings within spec, does anyone know?

Thanks!
Tom

 

Take the emulsion tubes out and look inside them. Hold them up to the sunlight.

Rotate them and see if the inside is smooth. If the motion of the needle has left a wear mark inside the tubes, replace them.

I had this happen to my Bandit 1200. Drove me crazy. Would idle perfect. Had a huge off idle to midrange stumble that made it almost impossible to ride. Once above 6k or so, would pull great to redline. But I had to fan the clutch to get the thing moving.

With new emulsion tubes, it runs as it should.