Compression

[Lonerbtw]

  Had a miss to start with. Cleaned carbs, low jets were pluged. Still miss and small backfire. Changed vacume lines, o rings and set carbs at 2 1/4 turns. Backfire gets worse. De smoged, ajusted valves(all good). This all started about 6 monthe ago with a hydrolock. Motor did lock up but did not get the starter. Pulled plugs, turned over and pushed the gas out, changed oil twice and rebuilt petcock. This happened on the left bank. Now is backfireing bad.on that side. Just did a compression test, Right bank 135,120,140, left side 60,60,65. and starting to smoke a little. Do not want to go to the stealer because when I took my wifes in to have a frount tire changed the mec. asked what kind of bike is that. then stated oh thats a Valk. I still had to retourque axel nut.
  Any ideas? I can understand burnt valve or broke rings but all three holes on one side. And it runs pretty good pulling in 4 th gear and cruising in 5 th. No backfireing.

[Chrisj CMA]

Im no ACE mechanic, but just thinking through it.....if all three on the left are low and seems, about the same, I think that brings you away from The idea that rings or valves are the culpret.  Im thinking maybe the head gasket.  It is one thing that ties all three cylinders together...........

[Lonerbtw]

  Thanks Chris. Went out pulled plugs. Put the guage on #2  checked it. 60 psi. put a plug in #4 and rerun test. 90 psi. Looks like that might be the problem. No water in oil or oil in water. What kind of job is it to pull the head and what should I keep an eye on doing it. Have worked on 750 Hondas for long time so know basics but its been awhile.
  Thanks Loner

[Patrick]

Just to make sure we know which side is which,, 1,3,5 are on the brake pedal side[right side]..  Which cylinder was fuel locked???  Generally if a head gasket fails, two cylinders may read low..  Something just doesn't seem right about this,,has an after market trigger been added??  Are you able to perform a cylinder or radiator leak test ??

[Chrisj CMA]

I think you need more diagnostics before you pull it.  If you do get enough indications for a head gasket the hardest part is maintaining the timing as you  put it back together.  I would not attempt this without a HONDA shop manual!!!!!!!  Hopefully somone that has been through this can not only confirm your symptoms/findings....but would be able to help with the tear down.......I dont think its that hard if you have tore engines apart before

[TJ]

I know someone will disagree but you need to pull the front cover and check to
make sure timing is set right.  you will probably fine the left belt off a tooth or two...

[Russell Rice]

My 99 Tour backfired and missed after desmog, taking 60 thousands off the heads and re- jetting the carbs. It ran great in 4th and 5th gear. Did not do compression test so I am not sure about that. Tore back into the carbs  and everything was ok. My Tour is a California legal and  had the canister and all the other smog stuff on it. The carbs had extra vacuum tubs coming off of them and I packed the tubs with lead and put vacuum caps on them and still had the miss and back firing problem. I bought some carbs that did not come from a California legal bike. I installed my jets on the new carbs and it runs GREAT! I believe there is something different that I did not know about on the California carbs when I did the de smog.
I do not know if that helps you out any but it sounds like some of  the problems I had.
Bike is still running GREAT!

[John Schmidt]

I agree with TJ. That's the first thing I thought of when you said all three cyl. are low. I'd sure check the simple stuff first before yanking the head. Like was posted above....a gasket will usually only affect adjoining cylinders.....USUALLY!!

[Lonerbtw]

 #2,4,6 shifter side. Dont know befor I owned it but I did not do a trigger wheel. Have had the bike for like 3 years. It was rearended so I triked it back then. Had trouble with carbs , pulled them cleaned and replaced. As stated no problems till hydrolock about 6,7 months ago. I am not sure witch cylender shot gas across the shop but I think it was eather 2 or 4 . I dont have the gauge to do a leak down test, I may have to build one. I will check the timing tomorrow . Thanks for all the input.
  Loner

[Madmike]

.. not convinced that it is a valve timing issue, I can't see the pressure attained at the transition from compresssion to power being effected by valve timing and so you should still see max cylinder pressure on the compression gauge as long as the Schrader valve is working - both intake and exhaust on that bank would be late opening and closing which would mean the intake closes a little late but it would be at the bottom of the stroke when the linear movement of the piston is minimal... 

..... try putting some oil in the cylinder and this should help eliminate rings unless they are completely gone....

...bent rods... anybody experienced this, it seems the starter fails before this happens ...?????

.... head gasket - maybe ----  perhaps pull the exhaust off and you may hear the compression from the adjacent cylinder coming out the exhaust port.....

[roboto65]

If you have a compression gauge do you have a air compressor you could do a leak down test attach the air to one of the low cylinders and see if you here any air coming out anywhere other than tha howmany miles on bike and when were the valves checked. Could be some VERY tight valves but that is stretching it.

[Robert]

I vote for the timing or broken piston ring landings, as already said leakdown test will help and wheres the air going listen to the air and learn. Make a adapter and hook up the air compressor to directly to the cylinder with a inline regulator then you can listen or even feel the exhaust intake or crankcase. Just a thought if you do the air test and can keep some compression in the cylinder you will be able to see bubbles come out of the radiator if it is a head gasket, which I think is a long shot.

[Patrick]

The reason for mentioning an aftermarket trigger was for valve timing/installation.. So, I would remove the front cover and check the valve timing marks to see if the belt has been installed correctly..If the marks don't line up,, you gotts a problem[but that usually happens on the other side].. Then I'd pressurize a cylinder or two or three and start listening..

[1fastbob]

Before selling my 99 Interstate I did the carb removal and rebuild for the 3rd and final time.   Before removal I did a compression test. I removed all the plugs and disconnected all the primary sides of the coils and I held the throttle in the open position and let each cylinder hit 7 times.  My readings were left side 140, 140, 140 and right side 138, 138, 135.  If you are in the 60's on one side I would suspect that possibly the timing belt has slipped a tooth or two or of course as stated above the head gasket could be bad.  You could also have some slightly bent valves.  It would surprise me if the issue was with the rings on just one side. The reading of 120 on the left side would cause me to wonder if there is an issue there as well.  More info would be great such as mileage on the Valk.

If it were mine I would readjust the valves and make certain it is done properly and proceed from there.

Also mine had a miss and cleaning the carbs and the jets did NOT fix it untill I replaced the jets.  If you just cleaned the jets it may be necessary to replace them to fix the miss.

Edit. Another thought....which side was the hydro lock on?  Could be bent rods, but all 3?  Maybe not.
Good luck with it.

Bob

[Lonerbtw]

  I know what you mean, had the carbs off 3 times myself. 58.000 now and I think 45.000 when I got it about 3 years ago. Have put about 2.000 on sence hydrolock. That was my first thought that the valves had tightend up. Went by the Clymer book and checked all valves. Thay were all good. Did not have to ajust any on eather side. I will pull timing cover this weekend and check that out. As stated I cant see head gasket on all 3 holes. Is there a timeing advance on this motor? The reason im asking is that it runs really smooth down the highway 5th gear 2.500 rpms. Cant hear any miss and no backfire. Seems the more load I pull the less miss and backfire there is. I am running rattle traps so I can hear them on the hiway. Thay were on the bike when I got it.
  Loner
 

[1fastbob]

The more load you put on the engine the more the carbs move from using the slow jet to more of the mains.  The running part of your problem points to partially plugged slow jets.  Did you clean the jets or replace them? My problems went away ONLY when I replaced the jets and I did use the #38 slows. All my problems were related to the #6 carb. The person that purchased my Valk I/S called and reported to me that after 1000 miles it runs like a new one.

My BIG concern would be the very low compression readings on the right bank.  Is it possible (no offense intended) that somehow you did the compression test improperly?  Proper compression test requires removal of ALL spark plugs and either the secondary wires (plug wires) be grounded or the primary wires be removed from the coils AND the throttle to be held wide open during the compression test and counting the compression stokes of each cylinger through 5 to 7 strokes each. Battery also must be fully charged to spin the engine fast enough for a reliable test. I have no way of knowing your level of mechanical ability is the reason I ask the questions.

Hope this helps

Bob

[Lonerbtw]

  Left side is low #246  Did the compression test corelecty but did not ground plug wires. Had the boots set so thay would not ark out. Not taking any offence at all. I have had many many 750 Hondas apart and there is not too much that I dont know about them but this is a different beast. I started working on them before computers and fourms and had to learn the hard way. Now it seems that I have alot of friends that are willing to help and give addvice and I thank you one and all. My wife calls herself an educated door nob. She just sits there and nods her head while I explain all the problems to her and most of the time it comes to me as what to do. But this one has got us both stumped.
  I will check timeing in the morning , its to hot to go anywhere near the shop today. Again thanks
  Loner

[junior]

how does your pipes look and feel? are the insides of the pigs sooty or oily,wet and tastes like antifreeze? you might just have a bad seal on your test guage, is it a screw in type or a rubber cone type?

[Robert]

How about a report how the plugs look when you take them out? It can still be bad floats allowing to much fuel into the engine washing away the seal in the rings.
0.006 inches for the intake and .009 for the exhaust is the correct specs. Is it possible that you adjusted the clearance to the 15 to 22 thinking it was inches? The reason I say this if the cam timing were off by allot then the valves would be bent and you should notice a clearance difference if the clearances were on and the same and you did this recently then cam timing may not be a problem. You may not be able to detect though if the valves were only marginally bent. In this case the only test will be wheres the air going?

[Lonerbtw]

  My guages have both in. and mm on the blade. Did not adjust any of them thay were all correct. Headed back to shop to check timming now. have been there setting things up sence 5.30. Will let you know how things check out. #2 and 4 plugs almost looked wet and darker than 6 but thay did not look to be fouled. My compression guage is new and the screw in type.
  Loner
 

[Robert]

If they looked almost wet then more than likely they are only hanging on by a thread and as such would only work half way decent at a higher rpm.  Again as you know signaling that there is a problem. They should come out tan to white not wet at all. You may try switching spark plugs to the opposite bank just to see the result.

[Lonerbtw]

  I know there is a problem. But what is it? Just checked timeing belt and dead nuts on. I have put oil in each hole when I started checking things out and no difference in compression. I just cant figure why all 3 holes on left side are so low and all the same. 60,60,65. It runs better at higher rpms. Top end of 4th and cruising in 5th (2500 rpms) cant hear miss or backfire.
  Loner

[Lonerbtw]

  Going to try to make a leak down gauge after I put everything back together. Let you know what happens.

  Loner

[Patrick]

And the engine has been run for a short time before the compression test ??  I think I'd pressurize some cylinders and listen to them before pulling anything apart.. But, it does appear that you have valve problems.. As long as you have a screw-in compression gauge it won't be to hard to 'adjust' it for air pressure from the opposite end..

[Ricky-D]

Ok, so here is something to try.

I don't understand why anyone would connect your problem to spark plugs but regardless of that, I have to say you sure have a strange problem.

Well, anyways here is something try.

Use some blocks and whatever to lean the bike the other way, meaning over to the right side, and do the compression test that way.

With all three cylinders exhibiting the same there is some common denominator that connects them all to that low compression figure.

***

[R J]

I know someone will disagree but you need to pull the front cover and check to
make sure timing is set right.  you will probably fine the left belt off a tooth or two...

I tend to agree with TJ on this one.

Check the belts.

 

[Ricky-D]

I know someone will disagree but you need to pull the front cover and check to
make sure timing is set right.  you will probably fine the left belt off a tooth or two...

I tend to agree with TJ on this one.

Check the belts.

 

reply #21!

[R J]

Ok, so here is something to try.

I don't understand why anyone would connect your problem to spark plugs but regardless of that, I have to say you sure have a strange problem.

Well, anyways here is something try.

Use some blocks and whatever to lean the bike the other way, meaning over to the right side, and do the compression test that way.

With all three cylinders exhibiting the same there is some common denominator that connects them all to that low compression figure.

***

Ricky-D, did I read somewhere up there it was a Trike?

[Ricky-D]

Ok, so here is something to try.

I don't understand why anyone would connect your problem to spark plugs but regardless of that, I have to say you sure have a strange problem.

Well, anyways here is something try.

Use some blocks and whatever to lean the bike the other way, meaning over to the right side, and do the compression test that way.

With all three cylinders exhibiting the same there is some common denominator that connects them all to that low compression figure.

***

Ricky-D, did I read somewhere up there it was a Trike?

You're correct!  Reply #8 included that information. I missed it!

[Mr.BubblesVRCCDS0008]

Just for grins I would remove intake tubes from that side of the head and run another test maybe something in airbox restricted. You could also observe the intake valve opening and closing.

[Robert]

Since you have the front cover off I would also take off the bolt that holds the cam gear on because I have heard of a few cases of the key breaking that holds the cam gear and cam in alignment it will take a couple of minutes. After this I would do the air or leak down test it will tell you where the leak is occurring. I know you adjusted the valves but I just have to ask the cam did turn correct? Just covering all the bases. Please switch the plugs too. Everyone knows internal engine problems on these bikes is rare.

Ricky the reason I asked about the plugs was 60 psi is really not enough to run on but I kinda wanted to cover all my bases that the plugs were so fouled that they were not igniting and allowing the gas to burn off and also bringing that cylinder up to normal temp. If its flooding or if gas is pouring in to those cylinders then the plugs never get a chance to come to life. I have seen times even putting oil into the cylinder didn't make a difference in a compression test under these circumstances. Because the oil was constantly washed out, Ive had a few Jags that this happened to and did a compression test with oil and no good found nothing really wrong except it flooded out. Had to put in fresh plugs cranked the thing for awhile and all of a sudden came to life. But it was the same thing 60 psi and all was well.m After running a few minutes compression came back up to normal.

[Lonerbtw]

  The last compression test I did last week. run the TRIKE for about 30 sec. turned it off and burnt my hand on all 3 pipes. Then started back up and run for about 5 min. to bring it up to temp. No gas smell in oil like washed out rings.  I did watch the valves open and close as I was turning it over to check the valve adj. I have put at least several hundred miles on it runing like this. It just runs so nice cruising down the road no miss ore backfire.  but 1,2,3 around town sounds like a friggen race car. I may just put it back together and drive it , when it lets go then I will know what to fix. Can you tell im getting upset with this thing.
  Loner

[Robert]

Can you tell im getting upset with this thing. sorry I know it sucks when your baby has a problem and you cant seem to get to the bottom of it. Rome wasn't built in a day, but I wouldn't continue to ride her like it is too long. If it is anything like piston landings then more damage can be done. Sorry I have to be the bearer of bad news. Your almost there just a little bit more to go.
 2 more simple things change plugs and the air in the cylinder test.

[Lonerbtw]

  Well the people from Oklahoma would be so proud of me. I built a pressure guage and it worked fine. Took timing up to 1,2 air leaked out exhaust, took around to3,4 same thing and the same on 5,6. While it was leaking I pulled the oil filler no sound from crank case. I also pulled tank and top of breather box no leak there eather. I then did the same thing on 1,3,5, and could not hear any leaks. Just to answer your question I have changed plugs twice sence this started and have swaped them once. What are piston landings, have not hurd that before?
  Loner

[Robert]

Well it seems you found your problem, it sounds like the exhaust valves are bent. It sounds like you did a good job but I am always a bit anal when it comes to diagnosing something. I would loosen the valves on those cylinders that you had a bad result from just to make sure the valves are closed and the air leaking isn't because of the adjustment or maybe the cam not being in the right position. If you do this and air is still coming out of the exhaust on one cylinder stop because you have to pull that head anyway. So it really doesn't matter if one is bent or all it has to come off. With these results dont worry about the piston ring landings they are the grooves in the side of the piston that hold the rings. They have been known to break. But that usually is in a supercharged bike the thinking was gas may have gotten in there and not compressed and caused some damage. When you do a confirmation and listen to the air the oil filter is not the place you will hear easier through the dipstick the fill hole or the crankcase vent easier. As for the air through the intake just open the throttle and listen or feel through the carb intake. I would feel better if we knew the reason the exhaust valves got bent so look for a reason. You dont want to do the whole thing and have a problem again.

[Lonerbtw]

  Thanks Robert. I did say oil filler not filter. But hay whats a t between friends. I will loosen all valves on that head and run test again. Could the hydrolock have caused this? Like I stated I have put about 2,000 miles sence that happened.
  Loner

[Patrick]

All the pistons were at TDC on compression [not exhaust] stroke when each test was performed ???  Sorry, just had to ask.. If that was the case and you have about 1/2 normal compression with air leaking from the exhaust system,, you gottz some exhaust valve issues.. Generally a bent valve will not retain any air,, generally.. Valves starting to burn will allow a bit of air to leak past them.. I'm wondering if someone happened to confuse the exhaust from the intake when setting the valves.. Still, being a Honda motor I wouldn't think the difference of just .003"  shouldn't hurt the engine.. Regardless, It does appear as though the cylinder head has to come off and the exhaust valves removed.. Thats too bad, I was hoping it was something a little easier and less expensive..
   OH, ring landings are actually ring lands..  And as stated they are the piston grooves the rings live in..They only break on these engines on the left side when a supercharger is installed,, I think from lack of manifold baffling..
   Sorry about the late response,, the board was down for a while..
 

[Lonerbtw]

  Well now im pissed.  I would have double checked anyway. I dont know for sure but I could have not done the valve timing check properly. I thought I did it to the book. I just loosened all valves on that side and did not get any air , intake or exhaust but could hear air going somewhere. Tightened down intake, could hear air, same on exhaust. Pulled dip stick and could hear air from there. So that means rings (right)? If so thats a job that I dont think I can do.
  Loner

[Patrick]

You will hear some air from the crankcase,, thats normal.. If the amount of air you hear sounds like a broken air hose, then, thats not normal..
Do you know how much you loosen the valves?? I would not have done that as long as you could feel some lash or maybe open them just a few extra thousands , but, if you really opened them you can figure out where to reset them by comparison to the opposite cylinder..

[Lonerbtw]

  I will reset the valves and double check this time. And run the tests again.
  Loner