Blue smoke om WoT and strange compression readings

[RempageR1]

Hi,

One of my fellow riders told me I am leaving behind blue smoke when I accelerate hard so this winter, I`m planning to fix that. First things that come to mind are the valve seals, my bike had been standing for 10 years when I bought it so they might have dried out but to verify I did a cold compression test. On cylinders 1, 3 and 4 I get 200 psi, and on 2 I get 180. After a squirt of oil, this one went up to 190. Readings are done with no carbs on.

Now my Haynes manual tells me 140 is good and the max is 171. So excess carbon could be the culprit. However I`ve run by bike this year with some cleaner additive so it should be clean. Also, the spark plugs have that nice coffee color and certainly aren't black. Mileage is also very good.

So what to make of this? I`ve checked with two compression tools (same brand) and both have these readings.

Has anyone else experienced values like this?

Thank you.

 

[Rusty McNeil]

Valves seals, guides or rings I suppose.
How many miles?
Your numbers are good and as you say a little high actually which carbon buildup will do. I got 175-180 on mine when it was stock.

Another thing might be the crankcase breather tube dumping oil into the air box. Are you using a stock air box etc. ??

When I went big bore, 13:1 CR stage 7 style setup, it took quite a but of sorting to build the right size catch can with the right size restrictors to stop it from putting oil into the carb. Had to ditch the stage 7 style breather with the hose going to the front carbs and run a catch can with open air breather.

When the engine was stock the normal stage 7setup was fine tho'

Changing valve stem seals will require removing cams, springs and buckets. It would take a better man than me to do that with the heads in place.

People have used compressed air to hold the valves closed ( in principle, regular car engines) but compressing the springs and removing the keepers fir our style heads would be the hard part. I haven't seen a tool that will do it without putting clamping force against the valve face too. (Big C-clamp style for bucket type setups)
But I've never checked to see if Yammy makes one to do that.

 

[bumper]

If your hell bent on doing the seals in the bike there is a tool that can be made to get the springs off after you pull the cams. You have to have a constant air source to put air in the spark plug hole to hold the valves in place after you turn the cylinder to TDC and lock it in place.

 

[Rusty McNeil]

If your hell bent on doing the seals in the bike there is a tool that can be made to get the springs off after you pull the cams. You have to have a constant air source to put air in the spark plug hole to hold the valves in place after you turn the cylinder to TDC and lock it in place.

For sure there is on the air pressure thing.

But what tool will compress the springs on an installed head?

 

[bumper]

I have a royal star standard, Yamaha should be slapped for what they did to those motors. No internal engine balancer and tiny carbs and weak springs on the valves. So we took venture cams and the double springs and put them on the royal star standards. Also made adapters to put the venture carbs on the standards. Big power improvement. Someone came up with a tool to bolt on the head to push the springs down. I will see if I can find the article/post of how to make it.

 

[Rusty McNeil]

I have a royal star standard, Yamaha should be slapped for what they did to those motors. No internal engine balancer and tiny carbs and weak springs on the valves. So we took venture cams and the double springs and put them on the royal star standards. Also made adapters to put the venture carbs on the standards. Big power improvement. Someone came up with a tool to bolt on the head to push the springs down. I will see if I can find the article/post of how to make it.

That's awesome. I was thinking maybe something that bolts down where the cam caps go. That woul be neat.

 

[Traumahawk]

They make tools like this for cars....so depending on the size...it should work on a bike...

 

[bumper]

wont fit, not enough room for it, its a flat bracket that bolts on, mine is in storage I will try and get over there and take a picture. And yes it bolts on where the cam caps are.

 

[wildweasel_pt]

If everything is normal and you get those compression readings i'd say a non standard head gasket? or resurfaced head?

 

[sdt354]

There is a new magnetic tool to remove the keepers with the heads on the engine. The frame might be in your way. Also, PCW has a nice tool that does work well with heads on and engine in the frame. Check it out under valve spring change tutorial. This also gives you a good idea of what's involved in changing seals. Though I think they complicated timing the cams a bit.
http://www.pcwracing.net/instructions/instructions.htm
Valve seals and guides usually show their ugly head also at start up after sitting for a while. Some smoke, with a good running engine and good compression. How much smoke we talking? A puff. That's a ton of time and aggravation for? +1 on building a puke can and connecting it up in a short amount of time. Nothing to loose.
Steve-o

 

[sdt354]

They make tools like this for cars....so depending on the size...it should work on a bike...

Sorry, not on ours.

 

[Traumahawk]

Sorry, not on ours.

Well means another tool that I will probably have to buy...lol

 

[Rusty McNeil]

They make tools like this for cars....so depending on the size...it should work on a bike...

That's precisely the type of toll that won't work on our bikes. Trust me I went through this.

Our springs sit down in a pocket with tight wall clearances. No tool that grabs the outside of the spring or the base of the spring will work.

 

[one2dmax]

I like the tool PCW came up with!

 

[bumper]

This is part of the tool, there is a small pipe that had to be made also. You can see the two holes that are threaded on top. A bolt goes in there to push down on the pipe that had a hole in the side of it. You then use a small magnet and pull the keepers out and release it by turning the bolt our and remove the small pipe and then on to the next one. It lets you do one cylinder at a time before you have to move the bracket to the next cylinder. The pipe needs to be big enough to allow enough room for the keepers. I am still looking for the pipe that I made. It is shown on a cylinder that is off the engine but this is the only way to get the springs off while the head is on the engine and in the frame. And the bolt you use cant be very long. When you look at the one picture you can see how far down in the head the springs are.

 

[Rusty McNeil]

This is part of the tool, there is a small pipe that had to be made also. You can see the two holes that are threaded on top. A bolt goes in there to push down on the pipe that had a hole in the side of it. You then use a small magnet and pull the keepers out and release it by turning the bolt our and remove the small pipe and then on to the next one. It lets you do one cylinder at a time before you have to move the bracket to the next cylinder. The pipe needs to be big enough to allow enough room for the keepers. I am still looking for the pipe that I made. It is shown on a cylinder that is off the engine but this is the only way to get the springs off while the head is on the engine and in the frame. And the bolt you use cant be very long. When you look at the one picture you can see how far down in the head the springs are.

That's really cool.

Maybe a narrow wall collar threaded on the outside would serve there, then could reach down inside from top to remove/install keepers???

Just thinking out loud...

 

[bumper]

cant find the rest right now. I had a pipe cut that was just long enough to get in there. I cut an inspection window or opening in it about half way down. I had a little cap that would set in the end of the pipe for the bolt to push on when I tightened it down. When the keepers came off it was easy to get them out with a little magnet end screwdriver. I Put grease on them when I went to put them back on to keep them in place.

I will keep looking for the rest of the setup

 

[mymax04]

blue smoke... could it be tire smoke? Ive seen mine do this & thought the same thing but it runs okay so I just figured it was the junk Dunlop I had on it smoking. Havent paid attn. now that I got new shoes

 

[RempageR1]

Whow this threat exploded

Since I need to have something to do this winter I am planning on taking the heads off. It still puzzles me that I got these compression readings, let`s see what I find when the heads are off. To be continued.

Edit: to answer some questions
- Mileage is unknown, 50K KM on the odometer but since I am still a bit out of spec with the biggest crank bearings it could have gone round a couple of times
- It`s not the tire. Got a nice radial on there.

 

[RempageR1]

Hi,

Well the first results are in. Head looks ok:

But the pistons seem to have way to much clearance:

Measured it at 0.40mm and according to my haynes that should be max 0.15mm

How to proceed? This probably means I need to go oversize pistons? Or just go for 1300? :confused2:

Thanks.