New member here, having problems with kz250d1 carb

First off, hi. I've used this forum for info in the past from time to time and I've never had much luck with the search engine, so I thought that I may as well join up with this build...

I have a 1980 kz250 d1 single with 1,600 miles on it. it has a keihin rk29 carb. I don't have the factory air box cover or the mount, so I'm using a pod filter.

The factory jets were; power jet:68 piolet: 35 and main:98

I am having a problem with the bike bogging/popping/sometimes dying under throttle(if it's sitting at idle, it will die if you try to give it full throttle, but will start right up), but she idles great. I have tried a 100 and a 106 main out of an old dj kit that I have,and it is still pretty bad. I've even tried shimming the needle .020 and then .040 with almost worse results. the plug is black now, but not wet, and the carb is very clean(it's been boiled)... The fuel screw is best at about 3 turns right now.

Am I missing something? Any suggestions would be great.

Matt

I think a 130 main jet, 40 pilot and 70 power with the needle raised could be a suitable starting point, but be prepared to do a lot of experimenting. Or get a stock complete airbox and use the stock jets and be done with it

matt_finish wrote: First off, hi. I've used this forum for info in the past from time to time and I've never had much luck with the search engine, so I thought that I may as well join up with this build...

I have a 1980 kz250 d1 single with 1,600 miles on it. it has a keihin rk29 carb. I don't have the factory air box cover or the mount, so I'm using a pod filter.

The factory jets were; power jet:68 piolet: 35 and main:98

I am having a problem with the bike bogging/popping/sometimes dying under throttle(if it's sitting at idle, it will die if you try to give it full throttle, but will start right up), but she idles great. I have tried a 100 and a 106 main out of an old dj kit that I have,and it is still pretty bad. I've even tried shimming the needle .020 and then .040 with almost worse results. the plug is black now, but not wet, and the carb is very clean(it's been boiled)... The fuel screw is best at about 3 turns right now.

Am I missing something? Any suggestions would be great.

Matt

Do a search for "Pods" then hope your computer doesn't crap itself!
You must re-jet for pods, and it may be more than what the results will be worth. If you have the stock factory air-box and boot in good shape, put it back with the stock jets and ride the Little guy. It will be much better.

.

check your electrical connections first

Make darn sure that the fuel service levels are correct per each carb bowl, and that there is absolutely NO LEAKS of any kind. Including the carb bowls overflowing internally (confirm on a bench overnight!) and air leaks.

Put the pilot air/mix screw back to default position and oil the pods properly (if required).

tune the air/mix screws accordingly, as the proper setting will not be the same across all carbs because of the pods.

Good luck.

In that ebay pic, it is the upper right rectangular piece, but i can't make out the pn. It doubles as the air cleaner mount and the battery cover as well. Thanks for that!

The bike is a single cylinder with only one carb, so this seams to be pretty critical compaired to the kz twins that i am used to.

I am all the way up to a 158 jet on secondary main, and it revs better, but still stumbles. Now, i am getting to where it doesn't like to start, but it will stay running once it does.

The coil input voltage was 12.66dcv when powered, and 14.42dcv with it running, so i am not seeing that as a problem right now. the plug is new, and it has a nice bright spark as well.

I may just swap it out with a non cv, i dont know yet...

I am also planning on running an upswept "martini shaker" exhaust, so i have the muffler replaced with a long pipe with a baffle from a 1100 shadow in the end for more flow. I'm not sure factory intake and jetting would be ideal in the long run.

matt_finish wrote: In that ebay pic, it is the upper right rectangular piece, but i can't make out the pn. It doubles as the air cleaner mount and the battery cover as well. Thanks for that!

The bike is a single cylinder with only one carb, so this seams to be pretty critical compaired to the kz twins that i am used to.

I am all the way up to a 158 jet on secondary main, and it revs better, but still stumbles. Now, i am getting to where it doesn't like to start, but it will stay running once it does.

The coil input voltage was 12.66dcv when powered, and 14.42dcv with it running, so i am not seeing that as a problem right now. the plug is new, and it has a nice bright spark as well.

I may just swap it out with a non cv, i dont know yet...

I am also planning on running an upswept "martini shaker" exhaust, so i have the muffler replaced with a long pipe with a baffle from a 1100 shadow in the end for more flow. I'm not sure factory intake and jetting would be ideal in the long run.

Personally I think you may be fighting a losing battle trying to swap the carb, pipe, etc. on a KZ250. Tuning it may prove to be a lifelong endeavor, and when you're done it will still have the power of a 250cc 4-stroke bike - not exactly going to set the world on fire. But, having said all that I sincerely do wish you the best of luck with the project. Below is a complete airbox drawing for your bike so you can more easiliy find part numbers. Ed

Thanks!

Sadly, more than stock performance is not my goal... the retro cool factor has won over, and i am more set on getting the "look". i am building this bike mainly for short city rides and the occasional vintage bike night meeting, so i have never wanted to get any more than 250cc performance out of it. i can have just as much fun doing 40mph on the curvy back road to my house as i do going ton up on the highway, so it will do me just fine with it's little powerplant.

This bike does share a piston with the kz1000, and the rest is basicly a klr250/klx250/mojave 250 atv engine with an electric start added and the kicker removed, so i guess there may be an aftermarket out there for go fast goodies...

Thanks again, Ed,for the good wishes. i always end up banging my head at some point when i venture into the unknown(by me, at least).

Matt

matt_finish wrote: Thanks!

Sadly, more than stock performance is not my goal... the retro cool factor has won over, and i am more set on getting the "look". i am building this bike mainly for short city rides and the occasional vintage bike night meeting, so i have never wanted to get any more than 250cc performance out of it. i can have just as much fun doing 40mph on the curvy back road to my house as i do going ton up on the highway, so it will do me just fine with it's little powerplant.

This bike does share a piston with the kz1000, and the rest is basicly a klr250/klx250/mojave 250 atv engine with an electric start added and the kicker removed, so i guess there may be an aftermarket out there for go fast goodies...

Thanks again, Ed,for the good wishes. i always end up banging my head at some point when i venture into the unknown(by me, at least).

Matt

I had a 1990 KLR250 and with a stock airbox and stock exhaust, I had the same problem, the bike, no matter what I did just didn't want to run right. It had a bog too, ran overall not poorly, but close. What I did was, replace the carb with a new one I found off eBay and it ran great after that. I'm not sure why, could have been because the carb was just worn out, but it fixed my problem I had. You might want to consider this if you can score a new (or newer) unit, then start toying with jets on that rig.

IIRC, the KLX250 have a normal piston type carb, and the engines are basically the same. Should be easier to jet.

OH yeah, I totally forgot to mention!

ALOT of people are not aware that Mikuni, Keihin, and DJ jets are NOT directly interchangeable, and the numbers have completely different flow rates!!!

Use this chart to figure things out, it really helps:



Good luck!