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Hard starting
#1
J
Jeff P51
J
Jeff P51
Hi, typically what is the compression of a 6.5 hp briggs engine? I checked mine and it was reading 30psi. It starts hard, but seems to run ok once started. I didnt think 30psi was even enough to start it. This engine,after priming 6 or 7 times, kinda chugs then dies a few times before it runs normally..any thoughts??
#2
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Rivets
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Rivets
Please post all engine numbers so we have some idea of which engine you are talking about. Briggs has built about a dozen different 6.5 hp models.
#3
J
Jeff P51
J
Jeff P51
Please post all engine numbers so we have some idea of which engine you are talking about. Briggs has built about a dozen different 6.5 hp models.
#5
R
Rivets
R
Rivets
First it would be nice if you would post all numbers, you’re missing the code number so we don’t know how old this engine is. Yes, 30 psi is low, but there are many things that can contribute to this. Bad head gasket, compression release problems, valves sticking, bad rings, etc. From your description I wouldn’t jump to a compression problem. If it runs fine once started I would be looking for a different cause. When you prime the unit, have you looked into the carb throat to see if fuel is actually entering the air horn each time you push the primer? You just have a bad filter base to carb gasket.
#6
J
Jeff P51
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Jeff P51
Its a head gasket...and yes a briggs will run with 30psi compression, but it starts hard..engine mfg in 2011
#7
StarTech
StarTech
First if you known it was a head gasket why did you bother posting other than to harass someone.
As for the compression reading it depend on your gauge set as automobile compression testers usually reads lower due the stiffness of the check valve spring and hose length.
But it would not hurt to check the valve clearances while you are at it. L-Head (side valve) engines tends to close up the clearances leading to a lost of compression. Plus with an ACR which this engine camshaft has, once it starts the compression climbs closer to normal operating pressures.
Btw the date code is important as Briggs does make changes through the year; not just at beginning of a particular year so your part numbers can be different based on when they made the engineering changes.
Personally I get tired of people acting it is a crime to give us the info we to help someone... They act they have stolen equipment and afraid they are going to get caught.
As for the compression reading it depend on your gauge set as automobile compression testers usually reads lower due the stiffness of the check valve spring and hose length.
But it would not hurt to check the valve clearances while you are at it. L-Head (side valve) engines tends to close up the clearances leading to a lost of compression. Plus with an ACR which this engine camshaft has, once it starts the compression climbs closer to normal operating pressures.
| Intake Valve | .005-.007 in (.13-.18 mm) |
| Exhaust Valve | .007-.009 in (.18-.23 mm) |
Btw the date code is important as Briggs does make changes through the year; not just at beginning of a particular year so your part numbers can be different based on when they made the engineering changes.
Personally I get tired of people acting it is a crime to give us the info we to help someone... They act they have stolen equipment and afraid they are going to get caught.
#8
J
Jeff P51
J
Jeff P51
Wow...I didn't know it was head gasket when I posted it. While waiting for a response , I hooked air up to block and found it leaking. Personally I dont appreciate your attitude. Then another guy says dont jump to conclusion that its a compression problem. Its got 30 psi...I think its a compression problem..
#9
J
Jeff P51
J
Jeff P51
Also it was a general question what is the TYPICAL compression of a Briggs 6.5..not really a question requiring a model number..which btw was never answeredFirst if you known it was a head gasket why did you bother posting other than to harass someone.
As for the compression reading it depend on your gauge set as automobile compression testers usually reads lower due the stiffness of the check valve spring and hose length.
But it would not hurt to check the valve clearances while you are at it. L-Head (side valve) engines tends to close up the clearances leading to a lost of compression. Plus with an ACR which this engine camshaft has, once it starts the compression climbs closer to normal operating pressures.
Intake Valve .005-.007 in (.13-.18 mm) Exhaust Valve .007-.009 in (.18-.23 mm)
Btw the date code is important as Briggs does make changes through the year; not just at beginning of a particular year so your part numbers can be different based on when they made the engineering changes.
Personally I get tired of people acting it is a crime to give us the info we to help someone... They act they have stolen equipment and afraid they are going to get caught.
#10
StarTech
StarTech
With an ACR present normally it should be at least 70 psi but a compression test on ACR engines is usually useless due the ACR action. This why Briggs and others engine manufactures say to check cylinder condition you should do a leak down test. And there is a modified version of this test that can be use on OHV engines as the base test only checks the upper cylinder where the modified test on a ohv engine can check all levels of the cylinder. It requires disabling the valve train which you can not do on a L-head engine.
Again we had to know the engine as some didn't have an ACR
Again we had to know the engine as some didn't have an ACR
#11
R
Rivets
R
Rivets
Briggs stopped posting cylinder compression years ago so there is no answer to your question. I asked for ALL engine numbers because the techs on this site (those with 20+ year of experience) use these numbers to to tell us more about the engine than 90% of the people who need help do. When questions are asked about compression you rely on past experience most time, not a spec. Being that we may be 1000 miles away you need to supply us with the info we request if you really want help. As I stated a variety of causes can contribute to a compression problem, but you gave us so little info that we had to fall back on guessing as to the cause. Another thing is that a major blown head gasket will not allow an engine to run properly after it is started, that’s why I suggested looking at a fuel problem. It’s time you back off and pull up your britches and start looking at your posts from our side of the fence. You are mad at us because we asked for more info which you didn’t give us. I guess you think it is our problem for not responding to your request in a manner that you feel you are owned. Sorry about that, but it doesn’t work that way. Time for us to get back the members who appreciate any help they get, as they pay us back with a thank you, even if the problem is solved by the time we get back to them.
#12
J
Jeff P51
J
Jeff P51
Not mad, disappointed. You are supposed to be professionals..maybe u should start acting like it. All I got was attitude. Im 61 years old, been working on small gas engines probably before most of you were born. I only ask questions to confirm my suspicions or get specs. Dont need techs on a power trip giving attitude...
#13
J
Jeff P51
J
Jeff P51
Oh...thanks for the help...and your wrong..the engine actually ran fine once it started
#14
R
Rivets
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Rivets
I’m well north of 70 so I probably was working on hit-n- miss engines before you knew what an engine was. Instead of giving us your suspensions maybe supply the info requested. If you are as experienced as you claim you would know that the better the picture you paint, the more help you get. If you really read my last post you would have seen that we know it ran fine after starting, which it will do if the heat gasket is not completely blown.
#15
J
Jeff P51
J
Jeff P51
Your post just confirms what I thought about you. I did nothing wrong. I asked a question. I was basically attacked by one of your other Techs, being accused of posting a problem I knew the answer to, which at the time of posting I didn't know..I run a small lawnmower repair shop part time in addition to working a full time job. Seems like maybe your heads are so full of crap, u forgot how to answer simple questions, like will a 4 cycle engine run on 30psi of compression..really, u need a model , code and type number to answer that? You reading out of a book? If your well north of 70, maybe its time to hang up your wrenches..
#16
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Jeff P51
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Jeff P51
Every tech or mechanic regardless of experience may from time to time run into a problem they are having trouble diagnosing. Its a good thing to have professional people you can bounce things off of to try and figure things out. Obviously this is not one of those places.
#17
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Rivets
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Rivets
This site has helped more people than you think. Bad mouthing the site and the professionals who volunteer their time and expertise shows the type of professional you are. If you are such a professional you would know that a 4 cycle engine will run on a lot less compression, as long as you can give it enough fuel and a very hot spark. The service techs on this site frown on making guesses when we try helping people with their problems, which is why we try to get as much info as possible to have a better understanding of what is going on. Remember we are not psychic or standing next to you with a strong drink in hand, which I doubt you would provide unless we paid for it, to see exactly what you are talking about. In your case I asked for model, type and code numbers because I wanted to see if your engine had an ACR. Finally every experienced tech in this industry know that when they need help, they go to other experienced techs to get it. They also know to get the best help you give your mentor as much information as possible, as there are always variances to the solution, such as brand, size, condition, use, etc. which they take into account before answering. As for telling me to hang up my wrenches, I would do so if there weren’t so many guys like you who still need training in this industry as how to repair equipment and handle different questions. Oh by the way, manuals and books are still used by us old farts, as they are most times more reliable than the internet.
#18
J
Jeff P51
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Jeff P51
Attacking me , insulting me and arguing with me shows how professional you are. I dont care how much knowledge you have. Now run along and try to help people instead of justifying your immaturity
#19
R
Rivets
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Rivets
Are you sure that your fingers didn’t push the wrong keys and you are 16, not 61, because you aren’t acting like an experienced professional. More like a teenager who can’t accept it when he’s proven wrong. I hope you don’t need help with any more equipment, as you have burnt the bridge with the good techs on this site. We’ve seen lots of DIY guys like you in the past and after being put in place they just disappear, which is what you should do. Bye, bye, bye, or should I say “see you later bro?”
#21
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slomo
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slomo
Okay, is this a new fresh engine or one that's mowed more grass than many others? Neglected oil changes? Never cleaned the cooling fins? Rough guesstimate is 30-140psi. You never specified engine condition.typically what is the compression of a 6.5 hp briggs engine?
Lack of maintenance for one. Sounds like you are fair with wrenches. Is the plug oiled down? Have you ever cleaned out the fuel tank? Ever installed new fuel lines? Ever checked the valve clearance? Bet lots of no's come up here.This engine,after priming 6 or 7 times, kinda chugs then dies a few times before it runs normally..any thoughts??
How did you confirm this?Its a head gasket
Nothing new to report here. Old news to most of us. Lack of compression could make hard starts, sure.and yes a briggs will run with 30psi compression, but it starts hard
If the primer is actually working, you are flooding the cylinder. Most every primer engine out there, requires 2-3 pumps. Many have stickers that state this very thing. Nothing in the engine manual that says 6-7 pumps for starting. So you are at fault here.This engine,after priming 6 or 7 times, kinda chugs then dies a few times before it runs normally
Again another inconclusive test. Was this air in the plug hole? Did you move the flywheel so the valves are in a closed position? Or just connect a hose and heard a leak? This tells us nothing.I hooked air up to block and found it leaking
I would swallow a bit and realize the gentleman trying to assist you has fixed more mowers than, well most of us will ever see. Lets all chill and get your mower running.Personally I dont appreciate your attitude
#22
J
Jeff P51
J
Jeff P51
Sir it was a blown head gasket..it now has 100psi compression , very little carbon build up in combustion chamber.Yes air in spark plug hole, Piston at tdc on compression stroke when air was introduced..put soapy water all around cylinder head..looked like a friggin bubble factory.6 to 7 pumps is what I was giving it in hopes of starting it. I know 2 or 3 should be sufficient. And number of pumps didnt really matter, it was going to start hard no matter what. Confirmed head gasket blown by removing head and visually inspecting gasket. Stevie Wonder could see it was damaged. The engine is back together, starts with one to two pulls with 2 or 3 pumps . of primer bulb...I could inspect valves and clearances but I dont see any reason to do so. Fuel tank clean..it only has one fuel line which seemed brittle and o replaced that before I even tried starting it. The mower was mfg in 2011...im assuming it has cut a few lawns.. dont really know its not mine..engine oil looked fresh, air cleaner was decent, looks like someone was taking care of it. Im guessing head bolts might have loosened up which may have caused head gasket issue...breather unobstructed.....anything else u think might have missed?
#23
S
slomo
Glad to hear you got her running.
S
slomo
Great news.Sir it was a blown head gasket..it now has 100psi compression
Fabulous.....Confirmed head gasket blown by removing head and visually inspecting gasket. Stevie Wonder could see it was damaged.
Sounds like it's starting fine. There is a reason to keep valves in spec. Just stating the obvious..I could inspect valves and clearances but I dont see any reason to do so
That was my next question. Were the head bolts loose. Nice catch sir.Im guessing head bolts might have loosened up which may have caused head gasket issue
Lapping the head and head mating surface prior to installing a new head gasket. Every one I've seen require lapping flat again. Keep the head bolts at factory spec once a year. Easy 12 second check. Some plate glass, 220, 400 and 1000 grit wet/dry paper. Let the paper do ALL THE WORK. Rotate the glass around while you are rubbing on her.anything else u think might have missed?
Glad to hear you got her running.