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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Cylinder compression /cgi-bin/YaBB.pl?num=1405503533 Message started by Thomas Högberg on 07/16/14 at 02:38:53 |
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Title: Cylinder compression Post by Thomas Högberg on 07/16/14 at 02:38:53 Hi everyone What should be a normal compression reading in kg´s? My local repairshop got 6 kg... He also said that it leaks through the exhaust valves. /Thomas |
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Title: Re: Cylinder compression Post by Gowor on 07/16/14 at 03:25:17 Kgs are a unit of weight, not pressure. If it was 6 kg/square centimeter, then you get about 85 psi, but I'm guessing here. I think a normal value is about 145-200 psi. Check if they disconnected the decompression electromagnet at the shop when testing. If not they'll get a very low compression and leak at the exhaust valve, because basically that's what the decompressor is for :-) One mechanic checked my engine without disconnecting it - he got a very low compression, and couldn't figure out how the engine works at all. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 07/16/14 at 05:29:31 537B637B66140 wrote:
You are probably right about the unit :) let´s see... for how long is the decomp active? until the engine runs? in that case I understand that there will be a low comp value if you check it without having the solenoid disconnected. |
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Title: Re: Cylinder compression Post by Gowor on 07/16/14 at 05:59:27 From what I checked, it disengages half a second after the starter begins turning. From what I remember, the guy who checked it got a very low compression on my engine ("too low for the engine to work"), and a normal reading after I told him to deactivate it. I'm not sure how he checked it though. EDIT: It's possible that in my case it wasn't engaged when he tested it, but adjusted incorrectly, so the exhaust valves weren't completely closed, even after it switched off. Anyway, since you have an exhaust valves leak, and the decompressor opens them, that would be the first thing I would check. |
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Title: Re: Cylinder compression Post by thumperclone on 07/16/14 at 07:33:34 ssm standard: 1000-1400 kPa 10-14 kg/cm2 142-200 psi limit: 800 kPa 8 kg/cm2 114 psi |
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Title: Re: Cylinder compression Post by Thomas Högberg on 07/16/14 at 10:40:50 153D253D20520 wrote:
Thanks you all for your help :) I will check if the wire is adjusted right. I do have a play at the rocker arms, both on exhaust and inlet side at TDC, so that leads me to believe that the decomp lever in the head can´t be that much wrong... |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/16/14 at 10:01:03 An update: after redone my valves and seats due to low compresson, 6-6,5 kg/cm2 (85 psi) I took the bike for a run and it´s still without any power.... it runs fine at idle and up to 50-55 mph if I am gentle but it would not accelerate good if I force it and it has no power actually. the bike has had this problem since I bought it this spring. Checked the compression today and it was 13 kg/cm2 (185psi) so the valve job worked out just fine :) K&N freeflow in airbox half spacer 47,5 jet if I remember correct, need to verify that. 152,5 main, a bit uncertain there as well, have been changing a few times... Dyna muffler, probably the california (cat) model, cause it has blued a lot at 5 inches from the downpipe. the bike is a -97 and has 33000 km (20500 miles) what would you guy´s do next?? /Thomas |
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Title: Re: Cylinder compression Post by Ed L. on 09/16/14 at 15:40:53 Check the cam chain adjuster and see how far it has moved out. At 20K miles it is time for a look. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/16/14 at 22:22:12 76576C7F1D330 wrote:
Thanks, I have modified it similar to a verslavy. /Thomas |
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Title: Re: Cylinder compression Post by HondaLavis on 09/17/14 at 20:56:37 Were the valve gaps set correctly after the seat job? Maybe your valves aren't opening all the way? |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/17/14 at 22:58:06 755253595C715C4B544E3D0 wrote:
I adjusted all four valves to 0,1 mm. |
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Title: Re: Cylinder compression Post by justin_o_guy2 on 09/18/14 at 00:05:22 What's that in thousandths? |
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Title: Re: Cylinder compression Post by jcstokes on 09/18/14 at 03:34:21 Just under 4 thou, I think. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/18/14 at 08:33:24 474E5E594246485E2D0 wrote:
Thats correct, sorry I´m not that familiar with inches... |
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Title: Re: Cylinder compression Post by justin_o_guy2 on 09/18/14 at 12:56:27 I should have just found a conversion table.. I'm not familiar enough with YOUR system. I apologize for that. I have spent some time today on various conversion tables. Fahrenheit to Celsius,MPH to knots and MPH, BUT I totally forgot to look at that one.. |
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Title: Re: Cylinder compression Post by Dave on 09/18/14 at 13:10:22 0.1mm so if: 25.4 mm is equal to 1 inch. 2.54mm is equal to 0.1 inch 0.254mm is equal to 0.01 inch Then: 0.1mm/0.254 = 0.003937 inch |
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Title: Re: Cylinder compression Post by justin_o_guy2 on 09/18/14 at 13:23:31 Well,thank you,Dave. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/18/14 at 14:21:07 as i wrote earlier I have modified my camchain adjuster similar to a verslavy, but I did not change the chain for a new one.. could the chain be stretched so much that it messes with the ignition timing, causing my problems? have tested with mainjets between 135 to 152,5 and nothing seems to work, no actual power and it does not rev as it should.. could it be the "ignitionbox" under the left sidecover that is broken? really thougt that fixing my valves and getting nice comp value was the solution... >:( any suggestions are welcome ;) /Thomas |
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Title: Re: Cylinder compression Post by justin_o_guy2 on 09/18/14 at 14:53:21 You sure the slide is not sticking? Have you pulled the air intake off and manually lifted it? You know it's a vacuum thing.. you might consider hooking up a test,put a hose on the carb and suck on it,I have no idea what it actually Takes to lift the slide.. But,there are some pretty smart guys here who just might have an answer for you. There Are vacuum test tools and a resourceful guy Can figure out ways around spending money. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/19/14 at 09:19:28 3F2026213C3B0A3A0A32202C67550 wrote:
The slide moves nice and easy... Would the bike even run as smooth at idle and be as easy to start if I have misaligned the camchain a teeth or two? |
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Title: Re: Cylinder compression Post by justin_o_guy2 on 09/19/14 at 09:31:32 I've never seen a motor that ran with the timing chain off one tooth. Not saying it can't happen,I just don't Know. Did this problem Start when you were doing something with the cam chain? |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/19/14 at 09:38:37 Bought the bike this spring, had not been running for a while, and was not running ok . The price was right and as I was rebuilding it bobber style I figured that new gas, cleaning the carb, new airfilter and new jets would do the trick... I was wrong :-/ |
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Title: Re: Cylinder compression Post by justin_o_guy2 on 09/19/14 at 10:54:38 Well,how does it run if you stop and just Take Off hard? A good running one should have enough acceleration to make you grin a little. What's an acceptable,Ohh say, zero to forty.. ooops uhh, 64.3kilometers per hour time guys? I was making it to 60 mph in real close to 6 seconds,but mine wasn't stock. Do you know how to get a hold of the guy who sold it to you? Maybe he can tell you what started it all..Just stay nice.. I don't know what is wrong,but it RUNS and doesn't sound like it's eating its own guts so I'm gonna say it's gonna be okay. Might wind up peeling the top off and looking at the timing,but I think you can check it without that. There are timing marks inside the plug on the left side. If those are lined up,And you're on the compression stroke,not exhaust,then with the piston at TDC compression the valves should be closed and be at,whatever you said,,.1mm,wasn't it? I know you adjusted the valves and they were closed when you did it,but did you check the timing marks on the crank shaft to get it there? Turning the crank the same way the tires roll? If you did all that then the crank and cam are as timed as well as can be. IMO even though the chain IS longer now,all that does is slightly retard the valve timing. As long as the cam lobes are not worn down it should run okay. You said you have modified the chain tensioner,,that is a good thing, but how close together are the chain sides now? Can you poke a finger in there? GUYS how much can the tensioner push a tired old chain? I know it can't be allowed to push the chain over till it touches,that would be bad news.. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/19/14 at 11:38:57 It does not make me grin :P I bought it from a dealer who traded it in for a job he did not get paid for, so I don´t think thats gonna help me. I´m aware of the timing marks, to bad I can´t doublecheck the marks on the cam together with the crank and piston at tdc. darn rubberplug ... gets me wondering if I got it right ??? Yes turned it ccw. and yes there is still space for a finger between chainsides. As you say, it runs and if I´m gentle it cruises... but no power or acceleration :-/ Thanks /Thomas |
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Title: Re: Cylinder compression Post by justin_o_guy2 on 09/19/14 at 12:26:10 You can "Prove"the timing. Pull the plug on the side and get it to TDC compression. If you have the valves set right BUT the adjusters on the intake side are set obviously different depths in the rockers than the exhaust side,the cam is off. I don't know if that's even Possible,but at this point,what have you got to lose? That's what I would do.. You might wanna pull the plug and rotate the crank,not with a ratchet,but a breaker bar or something you can control the crank and not allow it to turn any more than you want. You can rotate it 180* and look at what the valves are doing,rotate,inspect,etc. Be anal,analyze it. IF you go. Oops got to go.. |
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Title: Re: Cylinder compression Post by Ed L. on 09/19/14 at 13:26:20 How about the fuel tank pet c0ck? could be the diaphram has started to leak. If the cam is off a tooth I would think you would get some backfires through the carb or out the exhaust. Sounds like a fuel or carb problem not engine timing or spark. Is the carb put together right? I just rejetted my '02 and put the little plate in upside down. The bike would start but not run very well. Took a couple of hours to figure it out, the dimple goes down, not up. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 09/19/14 at 15:32:07 617E787F62655464546C7E72390B0 wrote:
Thanks for this, I will check this tomorrow :) Ed L, I´ve changed to a raptor I´m also leaning towards fuel or carb I really think that I have put it back just right, but I will check that as well. Feel free to suggest more, need all the help I can get ;) /Thomas |
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Title: Re: Cylinder compression Post by Thomas Högberg on 03/04/15 at 13:53:31 Hi all 2 workshops have now tried to find out whats wrong with my bike and failed... neither have found a solution :-( the carb has been checked a number of times and main jets between 135 to 152,5 have been tried with actually no improvement what so ever. bought a used "cdi" unit but still the same the bike will not rev as it should and has no power. it runs fine if I´m gentle and cruises up to 55-60 mph. what to do? |
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Title: Re: Cylinder compression Post by verslagen1 on 03/04/15 at 14:23:26 Have you checked the cam timing? 1 tooth off will cause this problem. If new chain, cam marks will align with head, used chains will be slightly up at the front at max chain stretch cam will be close to 7° retarded. |
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Title: Re: Cylinder compression Post by Thomas Högberg on 03/04/15 at 22:27:20 I thought I did when I assembled it.... So, now I have to tear the top down again you say.. Hmm, really looking forward to that ;) Thanks for your answer, suspected that this might be the problem. I did not change the chain, just so that I have understood, the front cam mark, closest to the frontwheel, will be slightly up? /Thomas |
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Title: Re: Cylinder compression Post by verslagen1 on 03/04/15 at 23:13:19 with the crank at TDC make sure the forward side of the chain is tight. you can see this 1 is ever so slightly high on the right side due to old chain. http://www.hunt101.com/data/500/medium/cam_line_up.JPG |
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Title: Re: Cylinder compression Post by Thomas Högberg on 03/05/15 at 00:03:46 Thanks verslagen1 I will open it up and check /Thomas |
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