Vintage Dirt Bike Q & A

Anything and everything about Vintage Dirt Bikes! After you Register, email nathan@alp-sys.com and let me know so I can activate you.
It is currently Thu Mar 28, 2024 7:02 am

All times are UTC - 7 hours [ DST ]




Post new topic Reply to topic  [ 2 posts ] 
Author Message
PostPosted: Sun Jun 03, 2012 3:56 pm 
Offline
User avatar

Joined: Thu Nov 11, 2010 5:21 pm
Posts: 2
My new to me 79 rm125 seems to have the carb setup bizarre: 260 mainjet (250 stock) needle clip second from bottom (second from top stock). It also had the optional B8 plug. So far I put a stock B9 plug and put the needle clip back. It still sputters at past part throttle to full throttle. I should be able to pick up a stock jet locally.

My question is why? Was this the hot setup in 1979? Will I cook the piston of I don't run mega rich? I get 150 PSI compression kicking with running shoes on, so hopefully thats OK.

Comments?

-doug

76 370 Pursang in pieces
79 RM 125
86 KX 250


Top
 Profile  
 
PostPosted: Tue Jul 09, 2013 6:48 pm 
Offline

Joined: Fri Apr 04, 2003 11:34 pm
Posts: 43
Location: Daytona Beach, FL
Doug,
With out knowing the history of the bike, it's hard to say about the jetting specs in your carb. It may have been at run at a higher altitude than where you live (just a guess). Sounds like the float needle may be worn. My '77 would start easily, but spit and sputter and bog at full throttle. Messed around with jets, needles, air screw, pilot jets, etc,,,, Put in a new float needle and she ran like a bat outta hell. Try that before making any radical jetting changes. If you do have to make changes, do them in small increments, then check the plug color. 150 psi is plenty of compression for a 125.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC - 7 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 18 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group