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 Post subject: Bike Bogs out...HELP!!!
PostPosted: Thu Aug 05, 2010 10:14 am 
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Joined: Fri May 14, 2010 12:03 pm
Posts: 4
Ok, I'm having a problem with my 1980 RM50. The problem is that it starts right up and idles great but when I blip the throtle it wants to die or bogs out until I let it off and its back to idling fine. If I blip it a few times it will rev high and I can twist the throtle and it will seem fine. Once I let off and let it idle for a few seconds then give it gas it will cut out and die unless I let off quickly. Now from a cold start it starts with no choke, if I try to start with the choke it will not start or if its idling and I apply the choke it will die. The problem seems to be between 1/4 and 3/4 throtle.

I have cleaned the carb with carb cleaner and I just took it apart again lastnight and used compressed air again to make sure the holes were all clean. The float seems to be adjusted correctly and its not over flowing from the float bowl.

Anyone have any idea what could be the problem??? It's driving me crazy and probably my neighbors too with all the reving :?

Thanks in advance!


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PostPosted: Fri Aug 20, 2010 6:10 am 
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Joined: Sun Nov 30, 2008 12:10 pm
Posts: 1010
Location: Connecticut, USA
By "bogging out / cutting out", do you mean a too-rich condition (lots of smoke, four-stroking/blubbering, black/wet spark plug, etc.) or too-lean ('snoring' sound, little or no smoke)?

Assuming too-rich (since your bike doesn't need the choke to start), it could be a worn needle or needle jet, which mainly affects mixture between 1/4 and 3/4 throttle. The needles are still available for both the RM50C and RM50N carbs, but the needle jets are not.

This problem screwed me up for months on my MR. Changing jets made little or no difference. If it is the needle jet and replacements are impossible to find, the only options are to replace the carb ($$), grind the carb slide cutaway (I've never liked doing it, but it works), or building up the needle straight section with solder and then sanding it down (I've never done this with a carb needle, but I've done it with plenty of other brass and copper things; if you screw it up, just replace the needle).

Ray

_________________
'74 CR125M (175cc), '75 MR175, '82 RM250Z, '08 YZ250F, '14 Zero FX electric, '14 Zero MX electric, '18 Alta MXR electric


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PostPosted: Sat Aug 21, 2010 10:48 pm 
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Joined: Fri May 14, 2010 12:03 pm
Posts: 4
well after it was running pretty good the other day it I couldn't get it started again. I pulled the plug and it was black and wet (fouled). I pulled the plug and cranked it a few times put the plug back in and it fired and ran. I don't really think it smokes excessivly though. I've been trying to lean it out with the air/fuel screw on the carb. I'll try to mess with it somemore tomorrow.

Ray, thanks for the info. I hope I can get it going with out too much work and it's just that I still don't have it adjusted correctly. I'll try to play with it tomorrow somemore if I get the chance and post if I figure anything else out. If nothing good then I'll post what I find out.


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PostPosted: Tue Aug 24, 2010 1:09 pm 
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Joined: Fri Apr 04, 2003 11:34 pm
Posts: 43
Location: Daytona Beach, FL
You may also want to replace your float needle and check the float height while you're at it. I had a similar problem with my '77 RM125B. It would fire right up, I could sit there and rev it up while in neutral, but as soon as I put it in gear and opened up the throttle, it would bog until I let off. It would then run ok at low speed and bog again when I gave it full throttle again. I tore down that carb and cleaned it so many times I lost count. I replaced jets, needles, clip position, air screw settings, etc... I finally replaced the float needle and reset the float height and now it runs like a bat outta hell (like an RM125 should) :)


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