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!

73 RT360 compression

  • Enduro nut
  • Enduro nut's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Posts: 107
  • Likes received: 34

73 RT360 compression was created by Enduro nut

So ive been fighting this RT360 for the past 2 and a half years now, i had DEET rebuild the stator since i was having ignition issues and now thats all solved and yet i still have issues which i think i have both carb and compression troubles. Im reading 105 PSI give or take on my compression tester. If you ask me that is too low for one of these monsters, what do you guys think?
08 Sep 2021 09:17 #1

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

  • Posts: 559
  • Likes received: 205

Replied by run103 on topic 73 RT360 compression

Does that bike have auto decompression
08 Sep 2021 12:24 #2

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

  • Posts: 6
  • Likes received: 7

Replied by Maxwell on topic 73 RT360 compression

I've also been having compression problems on my DT-400. My Compression Tests have varied between 100 to 110 psi. It would not start and I thought it might be a piston ring stuck inside the piston ring channel. I tried using Marvel Mystery Oil down the spark plug hole to soak the rings overnight. Next morning I cleared the oil from the cylinder and pressure jumped up to 135 to 140 psi and the engine started and ran several times during a 45 minute period.
Then it quit running and would not start again. Compression test went back down between 135 to 140 psi again. I've decided to not soak the piston rings again and just replace the rings and maybe the piston.
I think the soaking verified to me that I have a sticking piston ring problem. Hope you have good luck tracking down your problem.
I've heard compression should be somewhere between 120 to 150 psi to start and run.
08 Sep 2021 18:31 #3

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

  • Posts: 6862
  • Likes received: 2577

Replied by RT325 on topic 73 RT360 compression

I don't know what it should be but i can pretty much bounce on my RT2 360 kickstart i have now. But things will still run on low comp, just not run as powerful. If you pull the decomp open it probably has less than 100. My RT1 cylinder had horse & cart clearance with very little comp & even less with decomp on, just an easy hand push through, but started easy. By all means go in there & check things but i don't think its related to you not starting problem. If it is a starting problem--i'm confusing my self now. What's is it's problem--running starting idling?.
08 Sep 2021 18:58 #4

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

  • Posts: 10774
  • Likes received: 6293

Replied by MarkT on topic 73 RT360 compression

DT400 has auto-decompressor and different gauges can give wildly different readings. 

My DT50's get far less than 100psi and start and run fine.  Found that out the hard way on the first one when I rebuilt the top end and no difference in compression. 
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: Jack
08 Sep 2021 19:16 #5

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

  • Enduro nut
  • Enduro nut's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Posts: 107
  • Likes received: 34

Replied by Enduro nut on topic 73 RT360 compression

Yes this bike has the manual decompression release, however the factory one does not work i ended up buying an alloy art adapter to screw into the 2nd spark plug hole. Its not the decompression releases giving me fits i made sure on that. This bike is a long story but i know when i first got it she kicked over way harder but then shortly after it started kicking easier but i still could get it to start. I assumed that the bearings and top end got lubed up pretty good "after sitting for who knows how long" hence forth the easier kicking but i did have my suspicions.
I know prior to the stator being rebuilt and using a cheap coil i was having ignition problems which thats all sorted out now. When im able to make her run i can not get that thing to idle no matter what i do. ive cleaned the carb probably a good 30 times, the floats are in great shape and slide up and down easy, the jets are stock, i  replaced that little O ring in there. As far as i can tell the carb is fine but i do have my doubts. Right now my eye is on the top end.
08 Sep 2021 21:09 #6

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

  • Posts: 6862
  • Likes received: 2577

Replied by RT325 on topic 73 RT360 compression

Hmm, so if i read it right it was hard to kick--was that compression hard or tight to turn hard--then it got easier--was that before you got it running, just in the middle of kicking it got easier?. Or it ran, then was easier after that to kick over. Carb only needs to be cleaned once but then again i missed build up in my 250 on the emulsion tube inside because i didn't think it could or would build up the entire internal length with stale fuel residue--wrong--& it was grown to pretty much fit the fat part of the needle & all the way down to the jet setter. I probably didn't look there the time before its last long hibernation either so had me head scratching for a bit. Crank key still in one piece?. Video would be nice when it does runs to have a listen. My 360 has me stuffed kicking with no de-compressor fitted but thankfully starts ok even with increased compression it has with head mods.
08 Sep 2021 22:12 #7

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

  • Enduro nut
  • Enduro nut's Avatar Topic Author
  • Offline
  • Premium Member
  • Premium Member
  • Posts: 107
  • Likes received: 34

Replied by Enduro nut on topic 73 RT360 compression

It felt fine kicking it over when i first got it. Like no snags or anything it was just hard because these 360s have a lot of compression. Hard to remember everything since i been fighting her on and off for the past 2 years. I know i got it running fairly quick but still needed fine tuning like carb adjusting and point gap "it liked to shut off and has never idled". Sometime during the 1st month of owning it thats when i noticed it got easier to kick over. I run premix and use 32:1.
I tried firing her up the other day and it was a no go. I had it out id say a month or 2 ago and it was running awfully weird. Its hard to explain exactly how it was running but it sounded like it was missing but i know it wasnt, its something to do with that top end or carb. Seeing how ive been into that carb many times and everything looks good my best guess is top end. My LT2100 has the same amount of compression give or take so if you ask me thats kind of a give away but I figured id ask what the compression should be for one of these before i start ripping the top end off.
08 Sep 2021 22:34 #8

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

  • Posts: 6862
  • Likes received: 2577

Replied by RT325 on topic 73 RT360 compression

Oh well, it's not easy for us to help without being there sometimes. Keep in touch & best of luck.
09 Sep 2021 01:51 #9

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

  • Posts: 26
  • Likes received: 4

Replied by carter6787 on topic 73 RT360 compression

It sounds like your crank seals need replacing.
If they are leaking the compression will be down and the engine will not run properly.
11 Sep 2021 19:22 #10

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

Moderators: yamadminEnduronutMakotosunDEETVinnieDevinJames Hart