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!

1972 Yamaha RT2 360 Does this sound like detonation?

  • The3ngineer
  • The3ngineer's Avatar Topic Author
  • Online
  • New Member
  • New Member
  • Posts: 5
  • Likes received: 1
The bike doesn't want to cruise at a steady RPM/ speed and is making this pinging noise. The noise is louder and more noticeable in person. It doesn't miss a beat on acceleration. While cleaning the carb I noticed it has a 220 main jet instead of a 230. Does this sound normal (video)? I also attached a photo of the spark plug. 

Youtube video

 
Last edit: 12 May 2022 14:19 by The3ngineer.
12 May 2022 13:39 #1

This message has an attachment image.
Please log in or register to see it.

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

  • Posts: 11768
  • Likes received: 6969
Sounds normal to me. 

 
 
 
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: Sneezles61
12 May 2022 17:54 #2

This message has attachments images.
Please log in or register to see it.

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

  • Posts: 11768
  • Likes received: 6969
That letter to the editor is from 1972 or 73.
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: Brzn
12 May 2022 17:56 #3

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

  • Posts: 7783
  • Likes received: 2854
I think it sounds on the point of being lean at the revs in the video. How's the timing, 2.9 btdc & no more. Slightly less might be good. does she kick back harder than usual.
The following user(s) Liked this Post: Enduronut
13 May 2022 01:04 #4

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

  • Posts: 1268
  • Likes received: 909
I have 3 RT3s that are regular riders. Motors are the same as RT2. I have #260 main jet, 6DH3 needle with the clip in the middle position. They don't sound like yours in the video. But they don't run as smooth as my DT3s. As the old magazine article states I believe this is a characteristic of the RT3.
The hours spent riding my Enduros is not deducted from my life span.
13 May 2022 06:14 #5

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

  • Posts: 119
  • Likes received: 122
Sounds like an air cooled two stroke to me.

It is easy to get worried about the noises coming from an air cooled two stroke top end.  Is it piston slap? Maybe it's a little end? Soon you convince yourself that the big end has collapsed and the piston is hitting the head.
Many sleepless nights ensue.
Then you pull it down and find nothing.  Been there, done that.  

Air cooled two strokes make any variety of sounds, often at the same time, often not.  It's a regular orchestra going on, all amplified by the cooling fins.

My 175 has had new mains, rebore, quality piston and small end.  Everything else has been carefully checked.  Run on quality synthetic two stroke oil in the oil tank with a dab in the fuel tank too for good measure.

It sounded quiet at first start, but now everything has settled down 150 miles later, it rattles like a good un at idle.

Nature of the air cooled beast unfortunately.  It sounds terminal, especially if you are used to four stroke bikes, but it is normal.

Time to worry is if the engine starts rumbling or develops a heavy knock on the overun.  
13 May 2022 09:19 #6

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

  • Posts: 592
  • Likes received: 230
To me it sounds lean and the plug looks that way also. One up on the pilot and then start working on the needle position and the main jet.  Air screw can affect this also.  Jetting is so much fun.  These arn't too bad for main jet changes maybe up the main first and test
Doug
The following user(s) Liked this Post: Enduronut
Last edit: 13 May 2022 11:40 by run103.
13 May 2022 11:39 #7

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

  • Posts: 343
  • Likes received: 253
I do hear detonation occurring sporadically in the video.  It's a unique sound, hard to describe but I think you already know.  Just like you would imagine a small, powerful explosion would sound confined inside the combustion chamber.

Jetting and tuning these old bikes is remarkably challenging.  The air cooled big bore likes to ping even if you're just a shade lean.  It is difficult to find the perfect balance of clean, smooth running at low throttle openings without running into detonation at a high speed cruise.  The plug looks pretty good so I think you're not far off on the main jet.  I would raise the needle up a notch and see how it runs, fiddle with the pilot and air screw as needed.  I have resorted to making shims for the needle for cases like this where sometimes it really wants to be in between two notches.

For off road usage it's not as tough, you can run them a little fat and it's not nearly as irritating.  If you're cruising on the street you will probably find rich jetting to be a constant nuisance.  I know I do.
The following user(s) Liked this Post: The3ngineer
13 May 2022 17:28 #8

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

  • Posts: 343
  • Likes received: 253
This is out of my 360 this afternoon. Jetting is damn near perfect. Tops out in excess of 90 mph, cruises clean once warmed up with very little four stroking and no detonation.  

13 May 2022 17:32 #9

This message has an attachment image.
Please log in or register to see it.

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

  • Posts: 7783
  • Likes received: 2854
The speeds you guys quote on your bike are way in excess of what we'd ever get here. Must be all down hill tail wind in the US. All uphill & headwinds here.
The following user(s) Liked this Post: Pedalcrazy, Sneezles61
13 May 2022 19:53 #10

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

Moderators: yamadminEnduronutMakotosunDEETVinnieDevinJames Hart