facebook1 youtube1 twitter1 instagram linkedin1 pinterest1

NOTICE:  If you are not a free registered member of the site, you will not see the photos in the forum, and you won't be able to access our premium member content. Please consider joining our community! REGISTER AND MAKE THIS BOX DISAPPEAR!

Hard to start 250 Mx A 1973

  • erickz
  • erickz's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 42
  • Likes received: 3

Hard to start 250 Mx A 1973 was created by erickz

May need a foot replacement.....kick and kick eventually starts but hard to keep running. Fresh premix and a B8ES plug. Would a B6ES help (hotter)?
Any other suggestions??
Thanks
22 Sep 2020 16:13 #1

Please Log in or Create an account to join the conversation.

  • Posts: 443
  • Likes received: 161

Replied by Mauser on topic Hard to start 250 Mx A 1973

My little knowledge is to check the slow running jet, this keeps the bike running and handles the throttle between closed and 1/4 open. The little hole through the middle is very small, don't be tempted to open it up just make sure it's clear.
Yamaha RT2 360 ~ Honda XR650R ~ Yamaha DT175MX ~ Kawasaki KH400 ~ GPz550

23 Sep 2020 00:17 #2

Please Log in or Create an account to join the conversation.

  • Posts: 5670
  • Likes received: 2058

Replied by RT325 on topic Hard to start 250 Mx A 1973

Check the choke jet fixed drilling in the bowl cavity in the bottom of where the tube sticks down. Also what Mauser says above too. Bit of a guess without a video. Choke only works when throttle is fully closed. But there's a fine line between choke & when its had too much choke & making it worse. Also if the choke jet is blocked then opening the choke only opens an airway & will be even more difficult to start with no fuel being sucked. Bit of a wild guess though as could be multiple things. Had an MX250 new & was always an easy starter.
23 Sep 2020 05:38 #3

Please Log in or Create an account to join the conversation.

  • Posts: 9464
  • Likes received: 5392

Replied by MarkT on topic Hard to start 250 Mx A 1973

Stick with the correct spark plug.

A "hotter" plug won't make it easier to start but would overheat during riding... could destroy the engine.
1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250
The following user(s) Liked this Post: Rick C., Bigdog302, RT325
23 Sep 2020 06:41 #4

Please Log in or Create an account to join the conversation.

  • erickz
  • erickz's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 42
  • Likes received: 3

Replied by erickz on topic Hard to start 250 Mx A 1973

The primary jet was plugged up. Cleaned that out and it started right ran till the ignition gave up.....again.
Details to follow.
Thanks
30 Sep 2020 10:19 #5

Please Log in or Create an account to join the conversation.

  • Posts: 5670
  • Likes received: 2058

Replied by RT325 on topic Hard to start 250 Mx A 1973

Put a DT250 points mag & cover on it & ride off into the sunset--with lights!!.
Last edit: 30 Sep 2020 14:48 by RT325.
30 Sep 2020 14:47 #6

Please Log in or Create an account to join the conversation.

  • erickz
  • erickz's Avatar Topic Author
  • Offline
  • Senior Member
  • Senior Member
  • Posts: 42
  • Likes received: 3

Replied by erickz on topic Hard to start 250 Mx A 1973

Just installed an HPI ignition on it. Will start after lots of kicks then quickly die. More kicks and got it to run for a bit. Took the carb off and cleaned it ... got it to start but same issue - lots of kicks but won’t idle. Air screw is 1.5 turns out from seating, idle three turns out, plug is NGk B8ES. Thoughts??? Help!!
23 Nov 2020 19:22 #7

Please Log in or Create an account to join the conversation.

  • Posts: 61
  • Likes received: 8

Replied by MotoDave0 on topic Hard to start 250 Mx A 1973

I am not familiar with the HPI ignition. Is that a complete ignition? Are you getting good spark or is it out of time?. Again I am not familiar with HPI. I use the Powerdynomo ignition I believe it was a bolt on and done. Then for CDI replacements I use Fireplug from www.cdibox.com.
74 MX250 in a Profab frame
70 AT1 in a Trackmaster frame
72 RT2MX
72 DT2MX
74 MX360

Future rebuilds:
73 AT3
74 YZ80
71 JT1L 60
25 Jan 2021 00:20 #8

Please Log in or Create an account to join the conversation.

  • Posts: 404
  • Likes received: 459

Replied by Pete-RT1 on topic Hard to start 250 Mx A 1973

When it does start have you been able to keep it running until the engine is warmed up and if so does it idle ok then?
If you can get it warmed up, switch it off then try and restart, if it restarts easily then it might be the starter jet being blocked.
I'm not sure which carb model is on your bike but the Mikuni website is great for information and diagrams, the jet is probably non removable and located in the float bowl.
Yamaha RT-1
Yamaha CT1-B
Yamaha CT1-C
Honda XR250
25 Jan 2021 03:43 #9

Please Log in or Create an account to join the conversation.

Moderators: yamadminEnduronutMakotosunDEETVinnieDevinJames Hart