bigyellowthing Posted September 27, 2017 Share Posted September 27, 2017 So M6 and suddenly no go. Compression readings of 110 / 75 / 75 / 110. top end off nothing untoward . bas gasket weepy, carbs ok, fat spark, filled compression chambers with oil, then petrol no leaks at all. any ideas Quote Link to comment
Blubber Posted September 27, 2017 Share Posted September 27, 2017 Cracked or bad coils? They sometimes only show their faulty when hot Quote Link to comment
Swiss Toni Posted September 27, 2017 Share Posted September 27, 2017 Compression readings should ideally be within 10% of each other, so I'd have a look into no's 2 and 3 cylinders regardless. I'd also agree with Blubber, the coils may be breaking down. Quote Link to comment
no class Posted September 27, 2017 Share Posted September 27, 2017 Your compresion readings indicate a poor motor ....... anything under 90 psi is dead . Quote Link to comment
pigford Posted September 27, 2017 Share Posted September 27, 2017 Did you do compression readings on warm motor with carbs wide open? Quote Link to comment
bigyellowthing Posted September 27, 2017 Author Share Posted September 27, 2017 thanks guys 2&3 don't share a coil and wouldn't it affect both pots that share the coil (1/2 - 3/4)? Agreed compression way too low but can't see a cause ... Quote Link to comment
bigyellowthing Posted September 27, 2017 Author Share Posted September 27, 2017 compression tested on cold motor. I know it isn't ideal but 75 0n 2&3 is properly bad isn't it? Head gasket? If head gasket is the issue is this something that is a GSX 'thing'? The cam chain tunnel seemed 'dirty'? Quote Link to comment
no class Posted September 27, 2017 Share Posted September 27, 2017 (edited) Could be combo of valve seats and worn piston rings..... either way that motor is tired.....70 odd psi won't even create a combustion event so all the fuel and spark you throw at it won't do sqwat . Edited September 27, 2017 by no class Quote Link to comment
Swiss Toni Posted September 27, 2017 Share Posted September 27, 2017 4 hours ago, bigyellowthing said: thanks guys 2&3 don't share a coil and wouldn't it affect both pots that share the coil (1/2 - 3/4)? Agreed compression way too low but can't see a cause ... 2 and 3 do share a coil. As do 1 and 4. 3 Quote Link to comment
Blubber Posted September 28, 2017 Share Posted September 28, 2017 In my defense....I misinterpreted "suddenly no go" , as having a stalled motor. Should have asked for more information. Don't worry... Won't happen again. Quote Link to comment
Sheep Posted September 28, 2017 Share Posted September 28, 2017 Did you make a note of the compression readings after oiling the cylinders?? Quote Link to comment
bigyellowthing Posted September 28, 2017 Author Share Posted September 28, 2017 Sorry I am an eejut could indeed be a coil... 1&4 / 2&3 of course doh! Quote Link to comment
bigyellowthing Posted September 28, 2017 Author Share Posted September 28, 2017 didn't check compression with oiled bores. Strip down shows no damage to valves, pistons or bores. With compression readings and age of poor old girl, honing and new rings probably overdue... Quote Link to comment
Sheep Posted September 28, 2017 Share Posted September 28, 2017 Or big bore kit Quote Link to comment
bigyellowthing Posted September 28, 2017 Author Share Posted September 28, 2017 Any ideas which coils I could replace my elderly units with? Quote Link to comment
bigyellowthing Posted September 28, 2017 Author Share Posted September 28, 2017 Sadly big bore, lumpy cams, clever ignition etc. beyond budget... Quote Link to comment
pigford Posted September 28, 2017 Share Posted September 28, 2017 Do it proper & fit 3.0 ohm (green) Dyna coils! Quote Link to comment
Swiss Toni Posted September 28, 2017 Share Posted September 28, 2017 'Wot e said! Quote Link to comment
bigyellowthing Posted September 28, 2017 Author Share Posted September 28, 2017 I should've bitten that bullet already. maybe I should ask advice before diving in spanner first? Quote Link to comment
johnr Posted September 29, 2017 Share Posted September 29, 2017 (edited) did you check your valve clearances before stripping it? if the clearances were too tight then when it got warm your valves may have been partly open. seems an odd coincidence that they both had the same pressure. had you checked the valve timing was correct? Edited September 29, 2017 by johnr Quote Link to comment
Gsxrsam Posted September 29, 2017 Share Posted September 29, 2017 Leak down tester will give you answer...... Quote Link to comment
bigyellowthing Posted September 29, 2017 Author Share Posted September 29, 2017 I'm thinking that whatever the cause it won't do any harm to replace coils, rings and gaskets whilst doing some checking, honing and gapping. you guys are amazingly helpful so thanks again. I appreciate all your advice. 6 Quote Link to comment
bigyellowthing Posted September 30, 2017 Author Share Posted September 30, 2017 And.... Which gaskets / rings? Best Quote Link to comment
bigyellowthing Posted September 30, 2017 Author Share Posted September 30, 2017 And which gasket sealant? Is Yamabond the best, if so which product? Quote Link to comment
Swiss Toni Posted October 2, 2017 Share Posted October 2, 2017 Yamabond/Suzibond...or Wellseal. Go with what's the cheapest/easiest to get hold of! Quote Link to comment
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