Need help! Carb issues

     I bought a 2004 xr4 last year and it ran great other than being extremely hard to start which really annoyed me, so this year after doing lots of reading on this forum I came across the solution... put on a BSR 42 carb from the Polaris Predator. As background I have done all the suggested mods except for the one to the slider.

     So I did just that, I also did lots of reading on the jetting and all the other things that need to be done to get the set up just right. What I came up with was 50/190 and screw out 2 1\2 turns and needle on second from bottom notch for the elevation here in Colorado Springs (7000). So I did exactly that and when everything was installed it fired up only with me holding the throttle at about a quarter turn and if I let go it would stall, besides that when I gave it gas the bike would just chug along and stumble and adjusting the mixture screw made no difference what so ever. So obviously the set up that has worked for most other people did not work for me. So I then proceeded to change the various jets (tried a 52.5, a 185 and back to stock) but no real change, the 52.5 and stock pilot worked best but the bike is still not ride able and the mixture screw has very little effect as it runs like crap with it all the way in or all the way out. As well as not running well at all the bike is also smoking a bit which it never did before.

     Tomorrow I will likely go out and get some more pilot and main jets but not even sure which way to go , bigger or smaller? Any suggestions or help would be greatly appreciated. Or if anyone knows what can be done to the stock carb to make it easier to start I would consider that as well.



Was it a used carb? If so, did you take it apart and clean it before installation? DId you remove the fuel screw and clean that passage? Set float level?

The carb I bought was brand new so there was no cleaning required.

If it ran good with stock carb perhaps a modified cold start technique was all that was needed

My 97 xr400 was a bear to start and I considered a new carb until I learned a little trick now I have no reason to consider a carb change

If it is smoking I would think it was rich???

If it is smoking I would think it was rich



I was thinking the same thing that it is running rich, as well i was thinking that the chugging is due to the engine getting too much fuel but not sure.

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