b6100 D650 Compression Check

FishLife · Dec 2, 2018

So my low oil light is coming on at idle. Took the sender out an put in a gauge and getting 6 psi at idle and 9 psi at half throttle. After some research, I suspect the plug in the end of the cam fell out. However, before I start digging in I would like to do a compression check. It has 1700 hours but if something needs to be addressed, I would like to know up front rather than later. Especially after go through the trouble of replacing the plug I don't want to have to go back in. Really trying to get an over all feeling of the health of the engine. Has any one done a compression on the D650? can you check through the glow plug port or do you have to remove the injector?

85Hokie · Dec 2, 2018

I agree with the oil plug too.

Does it start ok with glow for a bit? Or does it huff and puff and blow a lot of smoke before starting and once running?

When running are you getting blow by ?

As for compression - harbor freight has a cheap kit ....and glow plug is easier to test from

FishLife · Dec 2, 2018

85Hokie said:
I agree with the oil plug too.

Does it start ok with glow for a bit? Or does it huff and puff and blow a lot of smoke before starting and once running?

When running are you getting blow by ?

As for compression - harbor freight has a cheap kit ....and glow plug is easier to test from

Starts fine. Tad bit of smoke at start up and not while running. also just a tad bit out the breather tube. From what I have read that can be caused by an injector flooding a cylinder. That's why I would like to check the compression. I wasn't sure if doing the compression check through the glow plug port would cause any negative results. Thanks I'm trying to self teach me to be a diesel tech. lol

thepumpguysc · Dec 2, 2018

Comp. check thru the GP hole is perfectly acceptable..
Your looking for "even-ness" between the cylinders.. anything over 300 psi will start a diesel.. & you really don't want anymore than 10% diff. between the cylinders..
Harbor Frt tools has a DIESEL compr. tester kit.. you cant use a GASOLINE compr. tester due to the hi compression of the diesel..
Good luck..

FishLife · Dec 2, 2018

thepumpguysc said:
Comp. check thru the GP hole is perfectly acceptable..
Your looking for "even-ness" between the cylinders.. anything over 300 psi will start a diesel.. & you really don't want anymore than 10% diff. between the cylinders..
Harbor Frt tools has a DIESEL compr. tester kit.. you cant use a GASOLINE compr. tester due to the hi compression of the diesel..
Good luck..

Thanks. I was at Harbor Freight today to get the oil pressure gauge. They pretty strict on the one 20% coupon per day so I was going to go tomorrow and get the compression gauge.

North Idaho Wolfman · Dec 2, 2018

A little blow by is perfectly normal on these guys.
Now if your getting oil, smoke or heavy blow by then you have an issue.

One major thing to note, if its sat for any length of time it's going to have blow by that might be cured by just a good running of it.

thepumpguysc · Dec 3, 2018

If u haven't gone again yet.. Take a GP out & use a metric "thread pitch gauge" to determine the thread size.. & MAKE SURE the kit had a GP adaptor w/ those threads..
IF NOT.. get a "thread die" to make your own threads..

North Idaho Wolfman · Dec 3, 2018

On the B6100 and B7100, an others with the 70mm same class of engines, D550, D650, D750, D850,D1850, V1200 it's easier to check the compression via the injectors, because the intake and injection pump block the glow plugs.
the "deluxe" harbor freight kit that I've got has the proper Injector adapter.

FishLife · Dec 3, 2018

Compression check update.......
North Idaho Wolfman, you are correct. Couldn't check from the GP ports. Not enough room. So had to check at the injector. The gauge reads in 10 psi increments so all seem to read within 5 psi dry. A little larger gap with a spoon full of oil. Here are the results:

Dry,
cylinder 1, 330 psi
cylinder 2, 329 psi
cylinder 3, 329 psi

Spoon full of oil.
cylinder 1, 420 psi
cylinder 2, 418 psi
cylinder 3, 410 psi

Not sure why the gap with the oil. But there are the result. From what I have read the compression (PSI) standard is 450 and compression lower limit is 325 psi. But, as i was doing the test, I noticed the top of the head bolts by injector 2, closest to the valve cover is broke off. It looks like it has been that way for a long time. So I guess it looks like i'm going to have to pull the head.

torch · Dec 3, 2018

FishLife said:
I noticed the top of the head bolts by injector 2, closest to the valve cover is broke off. It looks like it has been that way for a long time. So I guess it looks like i'm going to have to pull the head.

Not necessarily. Get a left-hand drill bit (Cobalt, M35 or M42 if possible) and an extractor. You may be able to remove the remaining bolt with the head in place, then just replace it with a new one.

FishLife · Dec 3, 2018

torch said:
Not necessarily. Get a left-hand drill bit (Cobalt, M35 or M42 if possible) and an extractor. You may be able to remove the remaining bolt with the head in place, then just replace it with a new one.

Man I hate those extractors. Ever time I have used one it breaks and what a pain it is trying to get it out if I could. May try it anyway. Thanks.

D2Cat · Dec 3, 2018

Is the bolt broken off below the surface of the head, at the head, a bit
above the head?

I've had good luck welding a nut or a piece of metal with a hole in it on a broken bolt to get them out. A wire welder makes it pretty easy, but I've used a stick also. Just have to have a steady hand when using rod.

FishLife · Dec 3, 2018

D2Cat said:
Is the bolt broken off below the surface of the head, at the head, a bit
above the head?

I've had good luck welding a nut or a piece of metal with a hole in it on a broken bolt to get them out. A wire welder makes it pretty easy, but I've used a stick also. Just have to have a steady hand when using rod.

About 1/16" above the top of the head. I was going to tig a washers to it and then a nut to the washer. That's what i was going to try first. I have done it in the past and have had good success with doing it that way.

Any thoughts on the compression test results?

D2Cat · Dec 3, 2018

"Any thoughts on the compression test results?"

If it was mine I'd quit thinking about the compression. They will probably be better after some running. The gauges never read higher then compression actually is, but they can read lower. Esp. the less expensive units from HF.

The worst reading you have is 410. That's a lot of wear to 325. That'll take years!!

Some of the real stubborn broken off bolts required to dowse them with ice water after the weld.

torch · Dec 3, 2018

FishLife said:
Man I hate those extractors. Ever time I have used one it breaks and what a pain it is trying to get it out if I could. May try it anyway. Thanks.

There's extractors, and then there's extractors. Quality counts for a lot there. Cheap Chinese ones are usually either too brittle or too soft. However, unless the bolt is seized in the threads, the left-hand drill bit will often be enough.

That said, if you have some bolt protruding, the welding approach is excellent. Not only does it provide something to grip, but the heat and the shrinking of the weldment both contribute to the cause.

FishLife · Dec 3, 2018

torch said:
There's extractors, and then there's extractors. Quality counts for a lot there. Cheap Chinese ones are usually either too brittle or too soft. However, unless the bolt is seized in the threads, the left-hand drill bit will often be enough.

That said, if you have some bolt protruding, the welding approach is excellent. Not only does it provide something to grip, but the heat and the shrinking of the weldment both contribute to the cause.

Ya I wouldn’t trust old Harbor Freight for those. Harbor Freight is good for some stuff but any cutting, drilling, tapping no thanks. I will say this though. I have a 72” Snap On tool box but I’m really liking the boxes that they have out now. I need a little more storage and I’m thing about picking one up.

JohnDB · Dec 3, 2018

D2Cat said:
"Any thoughts on the compression test results?"

If it was mine I'd quit thinking about the compression. They will probably be better after some running. The gauges never read higher then compression actually is, but they can read lower. Esp. the less expensive units from HF.

The compression test reading is affected by the internal volume of the adapter and hose to the gauge. A bigger diameter or longer hose will reduce the reading. So an accurate reading depends on how much your test equipment mimics the official Kubota gear.

Agreed, compression you've got isn't worth worrying about.

North Idaho Wolfman · Dec 3, 2018

Nope no problem with the compression, run it like you stole it!

FishLife · Dec 4, 2018

North Idaho Wolfman said:
Nope no problem with the compression, run it like you stole it!

Cool. Now on to the next repair or should I say repairs. Is the a complementary
Download somewhere for a WSM for the B6100? I looked in the Kubota books but only see owners and operators manuals for this model.

85Hokie · Dec 4, 2018

FishLife said:
Cool. Now on to the next repair or should I say repairs. Is the a complementary
Download somewhere for a WSM for the B6100? I looked in the Kubota books but only see owners and operators manuals for this model.

Covers all three - 5100-6100-7100

http://kubotabooks.com/AutoIndex/in...df&AutoIndex=ee0a37a1ed6f3fa74ae29ef5f7b51717

http://kubotabooks.com/AutoIndex/in...df&AutoIndex=ee0a37a1ed6f3fa74ae29ef5f7b51717

http://kubotabooks.com/AutoIndex/in...df&AutoIndex=ee0a37a1ed6f3fa74ae29ef5f7b51717

b6100 D650 Compression Check

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