Carbon Build up and Compression

[VMAX Eddie]

I finally got around to sticking a compression gage on my MAX and results weren't too bad, but not great.

The good news it I don't think I have any leaks and I'm still within the recommended range, pretty good for a 20 yo motor.

I am however at the top of the safe range, around 170 on each cylinder. I changed plugs about 3k miles ago and getting a decent amount of carbon build up.

I've spoken to guys who recommended using the enzyme treatment which I have been doing fairly regularly since last year. I think however there is a nasty build up inside my cylinders from the last owner forcing the compression way up.

So my question is what can I use to get that crap out of there?! Besides the green bottle enzyme treatment I add to damn near ever other tank of fuel I have also ran the lucas gas treatment through many times and even the marvel mystery oil.

I read about the ferarri blow out tuning where you run the engine for 20 miles around 65 mph and it will flush it all out if you have fuel conditioner in there. Well I've done that by now many times over. So what now?

I saw someone saying good things about putting Sea Foam directly into a cylinder and that blows the **** out. I'm a little leary of pouring someone right in there but I want these things clean without having to do a top engine job.

Anyone have any success? And with what?

Cheers!

 

[maleko89]

I use Rislone oil treatment in the crankcase (once per year) and BG44K in the fuel tank.

 

[VMAX Eddie]

I use Rislone oil treatment in the crankcase (once per year) and BG44K in the fuel tank.

You use the BG44K once a year as well or regularly?

 

[maleko89]

Yes, once per year. I split the can into 3 treatments and add each when filling up. It's very potent stuff.

 

[1st Shirt Maxer]

Have you tried adding marvel mystery oil directly into the carbs? I need a check on this one since I've only done this on autos but 15 years ago I would add MMO directly into the carb to help clean carbon deposits. I remember that afterward my vehicle would act like a smoke machine for about 20 miles, it was quite embarrassing but I never had any carbon issues. For the sludge in older motors I would add a gallon of diesel or kerosene in the crankcase, run the motor up to operating temps the drain immediately. I've never done either one of these on a motorcycle but since the max is carbureted, I thought of that from my younger days. Anyone have good or bad feedback on doing this.

 

[MaxMidnight]

Eddie, forgive me if I'm missing something here.

You have a motor that is within spec, i.e. compression at the top of the range, but you seem to be saying that you want to reduce it?

A couple of point occur to me:

1. Are you assuming that carbon within the combustion space has increased the compression? Given that the compression ratio is the volume of the cylinder at b.d.c and t.d.c. then (according to my befuddled brain) then reducing this space (with carbon) will also reduce the displacement (volume of air drawn in) thus the c.r. will not change.
2. Is the motor running badly?
3. Are you assuming that the gauge on your tester is accurate.
4. Can you see excessive carbon on the crowns of the pistons?
5. If you have heavy carbon build up then pre-ignition is possible - any suggestion of this.
6. Could it be a rich mixture generating the carbon you see on the plugs?
7. Could the good readings be due to better sealing of the rings as you have reduced deposits with all of the cleaners you have put through the motor?
8. Were you happy with the way the motor ran before you took the readings?

If the answer is 'yes' then don't worry, throw away your compression tester as you don't need it and enjoy riding one fit Max.

If 'no' then make sure the basics such as air and fuel filters, tank breather, fuelling etc. are correct before suspecting the c.r.

If the c.r. was causing an issue then I would expect you to either hear the pre-ignition or see evidence on the plugs.

 

[VMAX Eddie]

Eddie, forgive me if I'm missing something here.

You have a motor that is within spec, i.e. compression at the top of the range, but you seem to be saying that you want to reduce it?

A couple of point occur to me:

1. Are you assuming that carbon within the combustion space has increased the compression? Given that the compression ratio is the volume of the cylinder at b.d.c and t.d.c. then (according to my befuddled brain) then reducing this space (with carbon) will also reduce the displacement (volume of air drawn in) thus the c.r. will not change.
2. Is the motor running badly?
3. Are you assuming that the gauge on your tester is accurate.
4. Can you see excessive carbon on the crowns of the pistons?
5. If you have heavy carbon build up then pre-ignition is possible - any suggestion of this.
6. Could it be a rich mixture generating the carbon you see on the plugs?
7. Could the good readings be due to better sealing of the rings as you have reduced deposits with all of the cleaners you have put through the motor?
8. Were you happy with the way the motor ran before you took the readings?

If the answer is 'yes' then don't worry, throw away your compression tester as you don't need it and enjoy riding one fit Max.

If 'no' then make sure the basics such as air and fuel filters, tank breather, fuelling etc. are correct before suspecting the c.r.

If the c.r. was causing an issue then I would expect you to either hear the pre-ignition or see evidence on the plugs.

Well it's right up there at the borderline. 170-175. When I had the top portion pulled apart last year I noticed a heavy carbon build up looking down through the removed spark plug holes. I was worried I might blow a seal or something with the compression up at max and yes figured it's because of the carbon build up.

Overall motor runs good. No smoking, no oil leaks I'm at around 20k miles. Occasional carb popping but mostly when the bike is cold or running low rpms around a corner say at an intersection. Unless what I'm hearing is pre-ignition. The guage I got is a fairly good one. If you account for a +/- on it then could be lower. All cylinders do have the same reading, give or take 5 or so, so that's good. The plugs are coated with white and brownish grey and very dry. This is after about 3k miles on them. I took a wire brush and a very fine sandpaper to em last night and then checked the gaps. Put them back in and was running smoother.

I've had the bike going on 2 years now so I'm working through everything trying to get all the maintenance to 100%. Anytime I do work I go the extra mile to flush or clean or replace items as I go.

 

[COP RUNNER]

i I WAS ALWAYS TOLD BY A COUPLE OF GOOD MOTORCYCLE MECHANICS " THAT WHEN YOU DO A COMPRESSION CHECK ON A MOTORCYCLE WITH SLIDE CARBS. , YOU HAVE TO HOLD THE THROTTLE WIDE OPEN , WHILE DOING THE TEST OR ITS NOT ACCURATE "!

 

[SpecOps13]

Skullduggery's compression is right at 220 on all cylinders but it's meant to be there.
Oh that is with the throttle open and all plugs out. Strafer is in the 160-165 range.
I used to run MMO mixed with the gas, it does a good job keeping things clean.

 

[VMAX Eddie]

i I WAS ALWAYS TOLD BY A COUPLE OF GOOD MOTORCYCLE MECHANICS " THAT WHEN YOU DO A COMPRESSION CHECK ON A MOTORCYCLE WITH SLIDE CARBS. , YOU HAVE TO HOLD THE THROTTLE WIDE OPEN , WHILE DOING THE TEST OR ITS NOT ACCURATE "!

Yeah I did the test with throttle wide open. Took around 10 turn overs to get up to stable.

 

[[email protected]]

Have you tried adding marvel mystery oil directly into the carbs? I need a check on this one since I've only done this on autos but 15 years ago I would add MMO directly into the carb to help clean carbon deposits. I remember that afterward my vehicle would act like a smoke machine for about 20 miles, it was quite embarrassing but I never had any carbon issues. For the sludge in older motors I would add a gallon of diesel or kerosene in the crankcase, run the motor up to operating temps the drain immediately. I've never done either one of these on a motorcycle but since the max is carbureted, I thought of that from my younger days. Anyone have good or bad feedback on doing this.

I've used diesel to clean out a motorcycle engine after the bike was wrecked crossing a river and was completely submerged. It took a few cycles to get all the crap out of there but it worked.



Sent from my SCH-I405 using Tapatalk 2

 

[MaxMidnight]

... I was worried I might blow a seal or something with the compression up at max and yes figured it's because of the carbon build up.

Overall motor runs good. No smoking, no oil leaks I'm at around 20k miles. Occasional carb popping but mostly when the bike is cold or running low rpms around a corner say at an intersection. Unless what I'm hearing is pre-ignition. All cylinders do have the same reading, give or take 5 or so, so that's good. The plugs are coated with white and brownish grey and very dry. This is after about 3k miles on them. I took a wire brush and a very fine sandpaper to em last night and then checked the gaps. Put them back in and was running smoother.

No risk of blowing any seals as the pressure would normally be contained within the combustion space. It may be an issue if there was a lot of blow by the piston rings but in your case that is unlikely.
The issue with heavy carbon build up would be pre-ignition or if sufficiently bad it can stop valves seating properly.
If you hear a light metallic tinkling, normally under acceleration or the motor continues to run after it is switched off then you may have pre-ignition.
Too high a c.r. for the fuel can also give the same symptoms.

The question that I'm still kicking around is whether carbon build-up will affect the c.r.
If it is reasonable to assume that any build-up would be distributed evenly over the combustion space then I suspect not.
You would effectively reduce the volumes of the cylinder at both top and bottom dead centres so the c.r. would, broadly speaking, stay the same.

From what you say above it sounds like the motor is running well.

On that basis my advice, for what it is worth, would be to enjoy it as it is and leave well alone.
Over the years I have given myself all sorts of heart ache and unnecessary work trying to fix things that are only wrong in my head, the old adage, 'If it ain't wrong don't fix it' is great advice.

 

[sdt354]

Have you tried adding marvel mystery oil directly into the carbs? I need a check on this one since I've only done this on autos but 15 years ago I would add MMO directly into the carb to help clean carbon deposits. I remember that afterward my vehicle would act like a smoke machine for about 20 miles, it was quite embarrassing but I never had any carbon issues. For the sludge in older motors I would add a gallon of diesel or kerosene in the crankcase, run the motor up to operating temps the drain immediately. I've never done either one of these on a motorcycle but since the max is carbureted, I thought of that from my younger days. Anyone have good or bad feedback on doing this.

This does work-Marvel mystery oil or ATF, as does plain water. My yearly tune includes getting the carbon off the valves and chamber. A small stream poured directly into each carb with the motor running about 1800 rpm. Steam clean.

 

[maleko89]

This does work-Marvel mystery oil or ATF, as does plain water. My yearly tune includes getting the carbon off the valves and chamber. A small stream poured directly into each carb with the motor running about 1800 rpm. Steam clean.

I might have to try this. I've always been reluctant due to me being afraid of over-doing it.

How much water per cylinder do you think?

Mark

 

[sdt354]

I might have to try this. I've always been reluctant due to me being afraid of over-doing it.

How much water per cylinder do you think?

Mark

Just a steady dribble Mark. A spray bottle could also be used if worried about over doing it.
Steve

 

[maleko89]

Just a steady dribble Mark. A spray bottle could also be used if worried about over doing it.
Steve

Thanks Steve! Water is cheaper than BG44K lol.

Mark

 

[Thevmaxrider]

Sounds like someone has been running high octane fuel, and maybe some octane booster, because they have heard that it will make the bike run better. Run a half bottle of Techron through in your next tank of regular gas and see what happens. I make it a point to run Shell gas whenever I can as well because for some reason all my vehicles run better on it. Looked at my valves this week while doing my spring maintenance and they are clean as could be.

 

[Redbone]

Thanks Steve! Water is cheaper than BG44K lol.

Mark

You not kidding Mark, I've bought a bottle or two at over $25 per makes sure you absotively posilutely use every drop of that stuff!

 

[leroycp]

For heavy build up I have used, with good results, SeaFoam deep creep. Spray 3 - 4 second squirts into each vacumn port. It will smoke and even show any exhaust connection leaks. Start with a warm engine and when done drive the piss out of it. Should be happy by then

 

[VMAX Eddie]

I've used diesel to clean out a motorcycle engine after the bike was wrecked crossing a river and was completely submerged. It took a few cycles to get all the crap out of there but it worked.

So just run a tank of diesel through it!? Yikes!

Some other good ideas will test some things out. I think I said already but haven't gone into the carbs yet. Going to need to break apart some of these virgin areas and get everything to proper working condition. Any of you gurus mind sharing your yearly/bi-yearly maintenance schedules for your Max? Could use some tips. I put around 5k miles on mine last year and would expect about the same this year.

So far this season I've changed the oil, radiator flush (did 50/50 and water wetter instead of just 50/50 this year, keeps coming out milky but nothing in the oil), new front and rear tires, back break pads and fresh fluid in the rear reservoir (was nasty), and refreshed the plugs.