compression problems
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Seasoned HDF Member
Joined: Mar 2008
Posts: 5,134
Likes: 146
From: texas
compression problems
i should have known better than to post pics of my bike.i think i jinxed myself.
i start it up...sounds/runs normal.i dont get on it hard.....get about 3 miles out start to hear weird noises...an air noise and then a slight tapping noise......simialar to the sound of a helicopter just not that loud.i turn around head home....while turning around i realize power is not there.i limp it home.temp reading was around 130.i checked compression....rear was 50 front was 115.i sprayed some oil(penatrating oil is what i had on hand) with 0 difference.it also reached compression quickly.dont know exactly the miles since top end but i am sure its less than 2000.i tried breaking it in nice and easy as well.------------------------is ther anything at all left to do but tear it apart again?
i start it up...sounds/runs normal.i dont get on it hard.....get about 3 miles out start to hear weird noises...an air noise and then a slight tapping noise......simialar to the sound of a helicopter just not that loud.i turn around head home....while turning around i realize power is not there.i limp it home.temp reading was around 130.i checked compression....rear was 50 front was 115.i sprayed some oil(penatrating oil is what i had on hand) with 0 difference.it also reached compression quickly.dont know exactly the miles since top end but i am sure its less than 2000.i tried breaking it in nice and easy as well.------------------------is ther anything at all left to do but tear it apart again?
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Seasoned HDF Member
Joined: Mar 2008
Posts: 5,134
Likes: 146
From: texas
i noticed exhaust "soot" on the other side of the pushrod covers.i am guessing i did not do a good eneough job torqueing down the head.when i torque it down before i could not get torque wrench on the back ones(right side).....i had to guess by paying attention how much i turned the left side(with a torque wrench).i could have got it wrong....somthing happened.i dont want to throw in the towel and take it to someone but i am seriously thinking about it.i guess i might as well take my girlfriend there as well and let them service her too because that is what it feels like....but evidently i screwed up somewhere.
Intermediate
Joined: Mar 2009
Posts: 36
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From: Cincinnasti
Not sure about the "spray" penetrating oil. I think I would try to start her back up and get to running temp. then check compression again. If still low pull out the corresponding spark plug and pour about a teaspoon of motor oil in then do your compression test again. Not sure about this one but in cars, anything more than 10% difference in compression between cylinders is bad news. Maybe PG can help with this. good luck brother.
When you did the compression test did you have the choke plate fully open [pushed in so it is off], and the throttle plate full open [hand grip twisted to full throttle]? These are important - you get low readings otherwise.
The air noise could be a head gasket leak; could be leaking where you see the soot; probably in the low compression cylinder. If you have an air compressor you can set all the valves to closed then with a rubber tip on the compressor nozzle fill up each cylinder. You will hear a head gasket leak if there is one.
Crank the head bolts down as tight as you can; also the cylinder base nuts and the rocker cover bolts. Take off whatever you need to access them. Then try to run it again.
This can be very frustrating; maddening even. You are not the first to deal with this with your ironhead. It will work out OK.
The air noise could be a head gasket leak; could be leaking where you see the soot; probably in the low compression cylinder. If you have an air compressor you can set all the valves to closed then with a rubber tip on the compressor nozzle fill up each cylinder. You will hear a head gasket leak if there is one.
Crank the head bolts down as tight as you can; also the cylinder base nuts and the rocker cover bolts. Take off whatever you need to access them. Then try to run it again.
This can be very frustrating; maddening even. You are not the first to deal with this with your ironhead. It will work out OK.
Thread Starter
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Seasoned HDF Member
Joined: Mar 2008
Posts: 5,134
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From: texas
iron mick i did the air trick but i couldnt hear or feel air coming out anywhere.its possible that the soot i saw was from exhaust not being tightned up eneough.....i did have an issue with tat awhile back that i had forgotton about.
also after checking the pushrods trying to get closed valves...turning back wheel etc. i checked comp. and it went up to 100 quickly.....i try again and its back to 60...so i put it in gear and roll it a bit,check comp. again and at one time it showed 80 i beleive.the times it had higher pressure i could release it and try again to only be at 60 again.it wouldnt always show a higher than 60 only those 2 times.all others it was 60.-------what does this mean????
front cyl is 120 rear cyl 60(alittle higher than originally because i realized i had a slight air leak on my comp tester) it was done this time cold and with closed throttle----not the right way but it doesnt explain 60.----------does this make any sense at all to you??any ideas appreciated.....i am ready to ride and this is my only bike.
also after checking the pushrods trying to get closed valves...turning back wheel etc. i checked comp. and it went up to 100 quickly.....i try again and its back to 60...so i put it in gear and roll it a bit,check comp. again and at one time it showed 80 i beleive.the times it had higher pressure i could release it and try again to only be at 60 again.it wouldnt always show a higher than 60 only those 2 times.all others it was 60.-------what does this mean????
front cyl is 120 rear cyl 60(alittle higher than originally because i realized i had a slight air leak on my comp tester) it was done this time cold and with closed throttle----not the right way but it doesnt explain 60.----------does this make any sense at all to you??any ideas appreciated.....i am ready to ride and this is my only bike.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
Straydog13.........
On your first post I read the front cylinder pressure was 115 and the rear cylinder was 50. That told me your front was good and the rear was bad.
But, your last post has the numbers jumping all over the place. With such different readings it is impossible to come to any conclusion.
Are you using a compression gauge of the type that you have to hold it tight in the hole as you turn over the engine? If so, that may explain getting the wide range of readings.
Go spend a few bucks and get a compression gauge that screws into the spark plug hole.
You want to obtain truthful readings and you need a good gauge to do that. Also, you must test both cylinders using an identical method. You are measuring how much air is drawn into the cylinder and how much pressure is produced when the piston comes up TDC several times in a row.
I always open the throttle full and crank each cylinder test an equal number of times to keep all things as equal as possible.
1) Insert the gauge into one of the heads spark plug hole. Tighten it down like you would a spark plug. Have the other spark plug in the other head. (remove the plug wires)
2) Have the choke off. Open the throttle wide open. Kick the engine over several times. What does the gauge read now?
3) Put the gauge in the other head, put the spark plug in the just tested head, and do the same exercise as in step 2. What does the gauge read now?
Anywhere between 100 and 120 is good. More importantly though, is that the readings for both cylinders are close to the same reading.
If you have one cylinder reading 115 and the other reading 50 to 75, then right there you have a problem.
The great difference in readings tells us that there is a problem in the low cylinder. It could be valves leaking or bent, or rings gone bad or worse yet scuffed bore and a combination of all of the above conditions. That is a worst case however.
So first of all you need to get some good solid consistent readings before you can determine what to do............ pg
On your first post I read the front cylinder pressure was 115 and the rear cylinder was 50. That told me your front was good and the rear was bad.
But, your last post has the numbers jumping all over the place. With such different readings it is impossible to come to any conclusion.
Are you using a compression gauge of the type that you have to hold it tight in the hole as you turn over the engine? If so, that may explain getting the wide range of readings.
Go spend a few bucks and get a compression gauge that screws into the spark plug hole.
You want to obtain truthful readings and you need a good gauge to do that. Also, you must test both cylinders using an identical method. You are measuring how much air is drawn into the cylinder and how much pressure is produced when the piston comes up TDC several times in a row.
I always open the throttle full and crank each cylinder test an equal number of times to keep all things as equal as possible.
1) Insert the gauge into one of the heads spark plug hole. Tighten it down like you would a spark plug. Have the other spark plug in the other head. (remove the plug wires)
2) Have the choke off. Open the throttle wide open. Kick the engine over several times. What does the gauge read now?
3) Put the gauge in the other head, put the spark plug in the just tested head, and do the same exercise as in step 2. What does the gauge read now?
Anywhere between 100 and 120 is good. More importantly though, is that the readings for both cylinders are close to the same reading.
If you have one cylinder reading 115 and the other reading 50 to 75, then right there you have a problem.
The great difference in readings tells us that there is a problem in the low cylinder. It could be valves leaking or bent, or rings gone bad or worse yet scuffed bore and a combination of all of the above conditions. That is a worst case however.
So first of all you need to get some good solid consistent readings before you can determine what to do............ pg
Thread Starter
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Seasoned HDF Member
Joined: Mar 2008
Posts: 5,134
Likes: 146
From: texas
pinion i have the screw in kind.i didnt test with the throttle open because i was so far off the mark that it didnt really matter.i consistently got 120 on the front....testing it several times.i consistently got 60 on the rear except for the 2 times mentioned.i did not know what to make of that.
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Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
pinion i have the screw in kind.i didnt test with the throttle open because i was so far off the mark that it didnt really matter.i consistently got 120 on the front....testing it several times.i consistently got 60 on the rear except for the 2 times mentioned.i did not know what to make of that.
If the consistent readings are 120 and 60, then the sad news is something is not right in the rear cylinder.
You will have to at least remove the head and do an inspection. If the exhaust pipe on the rear cylinder was smoking badly you can expect to have to remove the cylinder as well.
If there is no noticeable smoke (compared to the front pipe) then look to the valves as being the problem of low compression.
Keep us updated on what the inspection reveals........... pg
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Thread Starter
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Seasoned HDF Member
Joined: Mar 2008
Posts: 5,134
Likes: 146
From: texas
ok i found the problem.when i did the air test my mind was set on head gasket leak so i guess that is why i did not pay close attention to the pushrods.i woke up last nite wanting to go out with a flashlite checking them......anyway i checked them this evening and one was really off.it had almost 1/2 inch freeplay at the most....guessing 1/8th when up.i often overlook the simplest things for the most exotic....i tell myself i wont do it again and i always do anyway.i dont know why it was not right...i did them myself less than 2000 miles ago i would not have thought i would have had an issue with them.that is something else i will start checking from time to time.now i can get back to my other ironhead problems...for now straydog very happy
---thanks everyone.
---thanks everyone.
