crigar
Weekend rider
Posts: 88
|
Post by crigar on Jan 7, 2024 11:42:38 GMT 1
Yes: leak test for several minutes. Spark plug colour? New spark plugs? Spark plug caps correct? Coil correctly earthed (no rust)? Reeds broken? Sorry but this is a translation.
|
|
|
Post by muttsnuts on Jan 7, 2024 12:55:29 GMT 1
ok back to basics, what's the compression pressures for each cylinder - I know you said "within tolerances" but what are the pressures ? I just checked on pictures I took and now I have a doubt being within tolerances... 75 psi on both cylinders. Too low isn't it? Not sure I did it correctly (not full throttle) Will redo it tomorrow. thats buggered, even with WOT it won't go up by much, be surprised if you get more than 85psi
|
|
|
Post by xian911 on Jan 7, 2024 15:02:05 GMT 1
Compression after running engine few minutes at idle. Left : 95 psi Right : 86 psi
NB : mesured with chinese tool. Comment added on jan 12:.Only relative value is relevant. With same tool my perfectly running 1987 1WT shows 90 PSI when cool
left exhaust 50° cooler than right one. no surge when spraying brake cleaner on left cylinder, input rubber, head
|
|
|
Post by abar121 on Jan 7, 2024 16:49:06 GMT 1
Top end rebuild time.
|
|
|
Post by xian911 on Jan 7, 2024 17:32:48 GMT 1
New pistons/rings and cylinders rebored.
|
|
|
Post by muttsnuts on Jan 7, 2024 18:50:44 GMT 1
New pistons/rings and cylinders rebored. what they have been, or your going to ? A fresh top end should read around the 125 to 130psi mark, don't stress if its slightly less or more, there are a number of factors that affect it but it should be well above 100psi no matter what
|
|
|
Post by vectisitch on Jan 7, 2024 18:59:18 GMT 1
Just to say if the compression tester is a cheap one you can't rely on those readings. I bought a cheap jobby off Amazon and got 60 psi on my 31k. Borrowed a Stanley one and got 125 psi
|
|
|
Post by xian911 on Jan 8, 2024 9:08:24 GMT 1
Just to say if the compression tester is a cheap one you can't rely on those readings. I bought a cheap jobby off Amazon and got 60 psi on my 31k. Borrowed a Stanley one and got 125 psi That's what I meant when I wrote 'chinese tool' as far as I remind also bought on A...n I will test on my others perfectly running LCs in order to have a reference.
|
|
|
Post by 4l04ever on Jan 8, 2024 9:38:46 GMT 1
Make sure only the plugs or the caps have resistors, not both.
|
|
|
Post by beardy on Jan 8, 2024 12:38:06 GMT 1
Just to say if the compression tester is a cheap one you can't rely on those readings. I bought a cheap jobby off Amazon and got 60 psi on my 31k. Borrowed a Stanley one and got 125 psi How did my Gunson fare?
|
|
|
Post by xian911 on Jan 8, 2024 14:39:05 GMT 1
|
|
|
Post by freddie19 on Jan 8, 2024 15:07:46 GMT 1
Make sure only the plugs or the caps have resistors, not both. Yeah, I always read this but it's a strange one as my genuine 7000 mile RZ350 has the original factory plug caps which are the resistor type and BR8ES plugs! This is how it came from Yamaha. 😁🤔
|
|
|
Post by vectisitch on Jan 8, 2024 20:43:19 GMT 1
Just to say if the compression tester is a cheap one you can't rely on those readings. I bought a cheap jobby off Amazon and got 60 psi on my 31k. Borrowed a Stanley one and got 125 psi How did my Gunson fare? Soz I remembered it as Stanley for some reason. Lol
|
|
|
Post by xian911 on Jan 9, 2024 10:04:22 GMT 1
To go further ... 1/ Since I'm in Belgium and Brexit ...where can I have (buy, rent, build) a leakdown kit ? 2/ What are the symptoms of a faulty labyrinth and what is the simpliest way for testing it? 3/ Is it possible that a failure of the labyrinth will only affect the left cylinder?
|
|
|
Post by beardy on Jan 9, 2024 12:00:35 GMT 1
Alan Kelly on this forum makes and sells leakdown kits. Hopefully he can help?
|
|
|
Post by midlifecrisisrd on Jan 9, 2024 12:53:38 GMT 1
As above, Al will sort you a leakdown kit
Lab seal should affect both sides really
Steve
|
|
|
Post by steeley on Jan 9, 2024 12:55:04 GMT 1
Hmmm , you are having a mare of this job .Just to cheer you up some more . Some years ago a friend of mine had a 350ypvs to have a look at for a chap who said there was a clicking noise coming from the engine . He also said it didn't go very well . It was fitted with a rebuilt crank and cylinders and pistons/rings were good ok .After chasing the clicking noise for some time , carbs , reeds , check power valves my friend thought it was time to open up the engine for a look see. Crank seals good and crank had been rebuilt with new lab seal . On measuring the lab seal it was found the o/d was slightly under size. When the engine was running it was moving left and right on the shaft making the clicking noise .The owner worked at an engineering company and machined a groove in the lab seal and fitted an o ring which sorted the problem .
|
|
|
Post by stanlc7189 on Jan 12, 2024 18:01:25 GMT 1
I had exactly the same problem and eventually found that the crank had twisted so much that at one point both pistons were moving in the same direction! Now here's the BUT..... mine was misfiring on the r/h pot. If you check and set the timing correctly, it sets to the l/h cylinder, so the timing on that cylinder will be spot on and the r/h cylinder will be out if the crank is twisted. With your bike misfiring on the l/h cylinder, I would argue it's not a twisted crank, assuming the timing has been set correctly.
|
|
|
Post by lcmarky on Jan 12, 2024 19:14:17 GMT 1
I had exactly the same problem and eventually found that the crank had twisted so much that at one point both pistons were moving in the same direction! Now here's the BUT..... mine was misfiring on the r/h pot. If you check and set the timing correctly, it sets to the l/h cylinder, so the timing on that cylinder will be spot on and the r/h cylinder will be out if the crank is twisted. With your bike misfiring on the l/h cylinder, I would argue it's not a twisted crank, assuming the timing has been set correctly. Interesting. Saw something recently on FB where a Crank pin had sheared so the Web was effectively rattling it's way around.
|
|
|
Post by xian911 on Feb 9, 2024 22:48:42 GMT 1
Today I did a first leak test. Lose of 2 psi within 25 sec. 5 psi to 0 in 2 minutes. Leak test 4L0 by xian911, on Flickr
|
|
|
Post by midlifecrisisrd on Feb 9, 2024 23:07:54 GMT 1
Inlet rubbers most likely
Steve
|
|
|
Post by 4l04ever on Feb 10, 2024 0:08:59 GMT 1
Spray water with washing-up liquid in around the engine to find the leak. It will bubble up where the leak is.
It could be leaking past the square pin holding the primary gear on the crank.
That is only a small leak, so probably not the main cause of your issue, but may be a contributory factor.
|
|
|
Post by midlifecrisisrd on Feb 10, 2024 0:35:17 GMT 1
I've had it leak there before
I now put a bit of 3 bond on the end of it
Steve
|
|
|
Post by 4l04ever on Feb 10, 2024 10:38:57 GMT 1
I coat the square pin with Threebond. Also use Threebond on the inlet gaskets and the inlet rubbers.
|
|
|
Post by davecroucher57v on Feb 10, 2024 21:15:38 GMT 1
plug caps./
|
|
|
Post by xian911 on Feb 17, 2024 16:23:07 GMT 1
Left crank seal leaks. But could it explain my symptoms? Anyway I have to open the crankcase. [video src=" Left crank seal leaking by xian911, on Flickr"][/video]
|
|
|
Post by 4l04ever on Feb 17, 2024 17:32:28 GMT 1
Make sure only the plugs or the caps have resistors, not both. Yeah, I always read this but it's a strange one as my genuine 7000 mile RZ350 has the original factory plug caps which are the resistor type and BR8ES plugs! This is how it came from Yamaha. 😁🤔 Probably a Friday afternoon bike. or they ran out of the correct parts... :-)
|
|
|
Post by freddie19 on Feb 18, 2024 0:54:29 GMT 1
So that means I've got two Friday afternoon bikes......🤔 as my LC2 was exactly the same!!! 🤣🤣🤣
|
|
|
Post by muttsnuts on Feb 19, 2024 10:15:19 GMT 1
Left crank seal leaks. But could it explain my symptoms? Anyway I have to open the crankcase. [video src=" Left crank seal leaking by xian911, on Flickr"] [/video] [/quote] that doesn't look like a genuine seal to me, looks like one of thecheapo ones you can get, either way, it needs changing To answer your question, yes that will cause the symptoms you have been experiencing
|
|
|
Post by xian911 on Mar 21, 2024 14:25:12 GMT 1
|
|