1976 mr250

[Bbizello]

I have a 1976 Honda mr250 that I got on a trade and it had low compression and I put a new piston and rings in it with a .40 over bore. And I also rebuilt the carb with a rebuild kit I purchased off of eBay but I believe the main jet is a little bigger then stock on the one that came out of the carb itsaid 110 on the top and the new one that came with the rebuild said 140 on the side or it assuming those are the sizes of the jets? Anyways I got it all back together today and used the gas my dad has for our trimmer that is mixed and it started right up and right fine just needed to be tuned a little it bogged down but I didn't want to mess with it I just wanted to ride around my yard sense I finally had the time to get it back together. And I have bell ray 2 stroke oil (it says power valve formula on the top I know my bike doesn't have power valves but will that make a difference?) and I mixed a gallon of gas with 4ounces of bell ray oil (32:1 ratio what I found on another thread on here that worked good with these bikes so that's what I used) and now with the new gas it will start but won't stay running and it sounds like it's either misfiring or back firing really loud I tried adjusting the air mixture screw up and down both and it didn't make a difference. Any help would be greatly appreciated it's really frustrating me and would like to fix it. Thanks!!!!

[Bbizello]

Anyone have any ideas as to what could be wrong???

[rayivers]

Check out the thread below for more info on your carb and possible problems/solutions. You can also search that site (and this one as well) for additional suggestions.

http://vintagedirtbikeforums.com/viewtopic.php?f=21&t=2691&hilit=mr250&sid=0b880da1daa0853688f5dd82b2117890

If I were you, I would pull the carb and put in a 105 main jet and 45 pilot jet, and set the air screw 2 turns out to start. The carb should be thoroughly cleaned, and the float height set to 20mm. I'd also order a 100 main jet, in case you need it later. An NGK BP7ES or B7ES spark plug should work well.

Main jets:

http://jetsrus.com/a_jets_by_carburetor_type/jets_keihin_99101-357_main_Hex_25-xxx.htm

Slow/pilot jets:

http://jetsrus.com/a_jets_by_carburetor_type/jets_keihin_N424-24_slow_29-xxx.htm

Shop manual:

http://alp-sys.com/honda-elsinore/manuals/MR25076/ShopManual76mr250.pdf

I use Bel-Ray H1R oil at 36:1, which may be the same stuff you're using. I love it.

Ray

[Bbizello]

Also would you know of a place to purchase a idle screw and air mixture screw? And also i have a feeling it wouldn't be a bad idea to replace the points if you know of anywhere i could order a set of those from?

[rayivers]

This place in Australia has the two screws (they both come as one set, P/N 16016-358-004 or 16016-395-004) - you may want to try and find a complete carb on eBay instead, as these are pretty expensive:

http://www.motoretro.com.au/honda_partnumbers_2.htm

RetroBikes has the 30200-358-004 points:

http://www.olypen.com/retro/30200-358-004

Ray

[Bbizello]

Is there any aftermarket carbs that would work better for this bike? and is there any form of an electronic ignition for it?

[rayivers]

CDI:

http://www.alp-sys.com/vintagedbforums/viewtopic.php?f=21&t=1794

Carb:

http://vintagedirtbikeforums.com/viewtopic.php?f=21&t=1637&hilit=mr250+mikuni&sid=0545b4103ba45d7d2c66400d14f4fa57

http://vintagedirtbikeforums.com/viewtopic.php?f=21&t=2141&hilit=mr250+mikuni&sid=0545b4103ba45d7d2c66400d14f4fa57

Ray

[Bbizello]

Is there no kit for a CDI? i believe my stator is all messed up but not sure on how to test it or anything... And i would much rather have a CDI then points, i know my bike now isnt getting any spark would a fouled plug cause that or would it still spark?

[Bbizello]

anyone??

[capt justin]

id get a new plug and try that

[Bbizello]

also does any one have more detaild instructions on how to gap the points? i tried reading the ones in the manual and doing it but i have a feeling i screw it up which could be another reason why it int wworking properly.

[JacobBurges]

Did you ever figure out a good procedure for gapping the points? Mine seem to open at arbitrary times as the crankshaft rotates. No change in resistance either.