New jets and rebuild kit installed,having issues

Bike is an 83 xj650. So I had a buddy install some 6 sigma jets to accommodate my pods and straight pipe. Put about 20 km on it snd ran pretty good minus the revs didn't come back down as fast as I'd like it to between switching gears. Anyhow took it out yesterday went about 2 km and it backfired like 5 times and died. Then it fired back up snd I made it back home. Any suggestions. ?

 

Ditch the pods put stock airbox back in. You are going to have a time getting this to work right, these carbs do not like large volumes of air.

 

If revs are hanging and not coming down, look up diaphragm piston stick-tion, basically you have to polish the brass Pistons so you have immediate engine breaking when you roll off throttle. You may also have a vaccuum leak where additional air is getting sucked into the sides of the carbs (via worn out throttle shaft seals), around or through the carb holders (via cracks in the rubber or worn out gaskets). It's difficult to track down if you have pods though, using a proponent torch or carb cleaner sprayed around those areas. Have you replaced throttle shaft seals and polished the diaphragm Pistons and the bore they sit in? Clunk test? Look up Church Of Clean? Forgive me if you already know all this.

 

No I have not done any of this. Thanks for the info I will try snd track down a leak by the carb cleaner tonight.I'll polish up the Pistons too.

 

But why would it just suddenly back fire and shut Down?then fire up again ?I thought mathe it was running lean. The plugs look a grey ish white color

 

After the carb is re-jetted you have to go in with colortune to balance out the fuel/air mixture and then do a carb sync then another color tune just for fine tweaking. The high revs is an indication you might be running lean. I did the same to my bike like 2 months ago.

 

Backfiring is gas that wasnt ignited and pops (tiny explosion) in your exhaust as it comes out. check the carbs, clean clean clean, wet set float levels, bench sync, then when you put them back on colortune and sync them. Problems should be gone. Unless you have a vacume leak in one of the seals

 

What is colortune. ?

 

Its a spark plug with a glass bottom that allows you to see the color of the flame from ignition. You use this to help adjust the air mixture screws on the carb. You would want the color to be blue right before it turns orange. then blip the throttle and it should still be blue with some hot spots (orange). White would be too lean and can blow a piston.
As a starting point close all the air mixture screws (lightly) and then turn each screw out 2.5 turns.

http://www.carbtune.com/colortune.html

 

when was bike running last before carb rejet?
Fuel cap vent clean?
Your Gas Cap and You
how is the fuel hose run any sharp turns which may kink, vacuum hose same thing.

sudden shut down of the bike could also be the safety switches, and related relays.
sidestand switch and sidestand relay

about 65$

tuning the carbs you can do this by doing plug chops part of what you go through with pods.
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html
your KIT is just a place to start
do you know what jets were and were changed to?
where needles changed too they will have to be tuned in by shimming them.

 

Pods are a tough way to go because tuning becomes difficult. However some here have had some exceptible results. Although not perfect because of air flow design change you might get close.
My suggestion would be to check valve clearances, wet set the floats and check xj4ever notes on installing pods and make sure the jets sizes are close to what he suggests. Bench sync and install and do a running sync. Do several plug chops and see if you can get some tan on the insulators. Remember throughout the rpm range you may have lean spots on the high end or lean on the lower end of the scale. Make sure its not too lean because that can burn pistions.
Best of Luck!
MN

 

Thanks for all the inputs guys . I got the bike last year and the carbs were pretty rough but it ran enough to try it. I got it for cheap luckily. I've never really had it running good. ..thud is the first time its ran for 20 kms tho. My mechanic buddy is going to check into the fuel air and also sync the carbs and whatever else it's going to need. I will check the vent on the gas cap tonight as well. I'd like to keep the parts as I've converted this bike to a bobber and it suits you nicely

 

Will also check for vacuum leaks

 

these slides are anodized aluminum, just wipe with brake cleaner, no abrasives.
there's a tab on those diaphragms, make sure it goes in it's slot

 

Does a bpr7es differ from bpr7es. ?I've got the bpr in mine. ..

 

the R means resistance plug 5K ohms

 

Good catch Polock! Does the '83 have Mikuni carbs?

 

750's & 650's have Hatachi carbs only the 550's & 1100's have Mikuni's on the normally aspirated engines.

 

There are many theories about how to get pods to work right and if they will give a performance gain. I say read as much as you can and try different setups. The main issue with pods is how turbulent the airflow becomes and the velocity it enters the carbs. This crazy wacky airflow forces the carbs to run lean forcing the carbs to be jetted to handle it and affects the diaphragm that raises the needle. Jetting is not always the first step or the answer in getting it to work. To me the first step is creative thinking. Try to find a way to control the airflow coming into the pods, eg velocity stack inside the pod, shroud around the pods or even having trimmed down sleeve that goes into the pod. The sleeve would be more restricting than controlling the air and it has to be trimmed to find the right length to work.

Once you have a plan of attack, re jet accordingly. You will also then have to play with the jet size and fuel to maximize RPMs/horsepower/torque through out the whole range. I only seen one person say they almost got it perfect on here. I don't remember his name but you might want to do a forum search to see if he can share his setup. Most people just want pods to look cool and don't bother tuning them.

Me? i did the sigma 6 jet kit and i plan on trying to fabricate a pseudo velocity stack, that i can slip onto the carb and have the pod over it. My thinking is a cross between a exhaust baffle and a velocity stack. Then i plan to tune the carbs by playing with all jet sizes.

Good luck on the venture and i recommend reading as many articles you can.

Google "velocity stack pods cv carbs" for some good reads. Not all will say to go for it.

A good place to start is:
http://www.dotheton.com/forum/index.php?topic=68929.0

Also as we all stated above. Get your carbs rebuilt properly and cleaned. If not your efforts will be futile.

 

Does the resistor effect the way the bike runs ?