Head Gasket Leaking?

[zigblazer]

How would I tell if my head gasket is leaking on my 2011 Venture Lite 500 4 stroke? I'm very familiar with Cars and Trucks, and I have seen many weird ways that head gaskets fail. Some push coolant out, some burn it. One of my trucks with the duramax, would dump a certain amount of coolant then loose more very slowly, and just hold pressure in the cooling system for days after driving. Very similar to what this sled is doing. I've worked through most of the problems I've found with it, but have a couple left. It does not like to idle, which someone suggested might be the valve adjustment, but maybe it has something to do with a head gasket leak.

It idles great cold. But will slow down and die after 5-10 seconds of idling when I'm out riding. I had it up to temp and idling great once in my shop, but could not get it to do that again. What makes me think it might be a head gasket is the coolant. My rides have been 70-140 miles at a time, averaging 20-30 mph. Usually with a stop to eat at some time. I flushed the cooling system when I first got the sled in December, and replaced the thermostat. I tried like crazy to bleed the system, burping air out of every connection I could get to. After every ride I have to add 10-14 oz of antifreeze and release air from the tube fitting below the tank. I did once bleed by lifting the back and RH side of the sled to extreme angles. Also tried filling a funnel going into the tank and running a clear hose from the bleed port into the funnel. Ran it 3 times up to temp and cooling over night before I was completely convinced there was not possibly any air left trapped in the system. But after the next time I rode, same deal, needed to add coolant. It is also remaining pressurized the next day after riding, which is a classic sign of a bad head gasket in the duramax, due to air slowly added to the system through the leaking head gasket.

My season is officially over. Some trails are still open, but our temps are going to stay up starting Friday, and season official end date was 3-31. I would like to have the sled all ready for next year, not be chasing problems all season again. I will for sure check the valve clearances, but need to figure out the coolant loss and idling. I've already rebuilt the engine from my pickup and did the head gasket on my skid steer this year. I almost want to pull the head off, just to know for sure that is not the problem. Then the valves would get adjusted, as well as the head rebuilt, at the same time. But I would be very unhappy if I did the head gasket and it still used coolant and wouldn't idle next year. I put on almost 800 miles this year.

 

[RobX-1]

Have you pulled the plugs yet and compared them? If the head gasket is only leaking in one cylinder, that spark plug would look different.

When I had to replace the heat exchanger in my Apex, I ended purchasing one of these coolant vacuum/leak tester. Not only can you use to refill your coolant but can also use it to check for leaks. This kit does have one of its adapters that fits into the coolant reservoir and I had no issues purging my old coolant and flushing with new.

 

[zigblazer]

I have not pulled the plugs again. Pain since you need to take the gas tank off to do it, but that is the plan next week. That is a good idea on vacuum testing. It may hold pressure for days, but that isn't the direction of the leak if there is one. I bet I have enough tools to find a way to vacuum test the system. Wonder how much vacuum it can stand before all the hoses collapse. It may not show a problem even if it is leaking, but it might.

 

[RobX-1]

Totally understand about the lack of ease of access to get to the spark plugs on these 4-strokes but other than that, not sure if there are other tell-tale signs of a bad head gasket.

Although you will see some of the hoses up front around oil tank collapse while its pulling vacuum, the hoses for the rear exchanger do not nor does the hoses on the other side (underneath the clutches). The directions state to pull between -20in/Hg to -25in/Hg of vacuum, shut off valve, and then wait approx. 15 minutes to ensure pressure doesn't drop. I also wanted to flush the coolant in my other Apex so knowing I had two sleds to do as well as knowing I can also use it for my vehicles, it helped justified the cost of the tool.

 

[turbogts22]

You could try using a combustion leak detector on the cooling system.

Block Tester BT-500 Combustion Leak Test Kit - Made in USA https://a.co/d/7cbcUXu

 

[zigblazer]

Why didn't I think of that? That would be a definitive way to tell if it is leaking. I guess because I knew about the test but have never used one myself.

Thank you.

 

[Mooseman]

I tried using one of those and it didn't show anything. Mine would blow coolant out of the overflow hose only at WOT under load. Confirmed this by putting the end of that hose into a bottle and it would fill up after riding it hard. Replaced the head gasket and all back to normal. The head gasket was acting like a one way valve, letting combustion gases out but not letting coolant into the cylinder. compression was a little low in one cylinder but not overly. It did need a valve adjustment as all were too tight.

 

[zigblazer]

Did you have your head rebuilt when you did the gasket?

 

[Mooseman]

I did it myself. Check the last post. There are videos on YT on how to resurface the head yourself but you can have it done at a machine shop. Also good to check the valves are sealing right.

RS Venture GT losing coolant

Related to RS Venture GT takes forever to warm up, now I find myself losing coolant. To recap, it had low coolant with no obvious leak, replaced the thermostat, refilled and it idles fine and gets up to temp and pressure. I also installed a temp gauge and bled the system of air (had it...

ty4stroke.com

 

[zigblazer]

I took the head off. Combustion gas tester started turning yellow (positive for gases) after a few minutes of running/revving. Gasket had one section that looked suspect and may not have been sealing perfectly against the block. Guess I won't know until I get it back together, and probably not for sure until next winter out on the trails again. Looks like I ripped the whole thing apart, but it only took a couple hours to get the head off. But with the seat, handle bars, gas tank, and hood off there isn't much left above tunnel height.

Dropped the head off at a machine shop. I'll check the deck for warpage before I put it back together. I didn't think to check valve clearance before taking it apart, but will set it going back together.

I can try to post when it is all back together. Sure are small valves compared to what I've worked on recently. And cute little camshafts.

Also planned on rebuilding the primary clutch and replacing the front suspension bushings while I was at it. That didn't go as planned. I used the clutch rebuild kit and suspension bushing kit from dennis kirk. Clutch kit didn't have weight bushings, not sure if they are replaceable on this clutch. Suspension bushings didn't fit any of the worn out A-arm spaces, finally found that they fit the ski mount/pivot location.

I did find that one of the exhaust clamps had fallen off, no cinch bolt. Other than that I didn't find anything else needing attention.

 

[zigblazer]

 

[zigblazer]

Took almost 2 months to get the head back from the machine shop. I checked valve clearances and ordered the necessary shim blocks to adjust, and they came last week. Put the head on today, and tried to get the timing set before I gave up for the day. New shim blocks set valve clearance perfectly, but I had a small problem with the timing chain. Tensioner was easy to figure out, exhaust cam assembly took a little longer to figure out.

I don't know if the chain is extra loose because there is no oil helping hold the chain tight, but the spring in the tensioner is not strong enough to prevent the chain from slipping on the intake cam when rotating the crank. It has just enough play to jump a tooth, and I made darn sure the tensioner was preset, installed correctly, and freed to take up the slack. I think it will likely be fine once it has been run, and oil pressure helps tighten everything up. Then the lock spring will hold tension on it when it is not running.

Has anyone else had this problem when going back together?

 

[zigblazer]

I pressurized the oil system, even that didn't tighten the chain enough. It still slips when turning the crank. I'm afraid to finish putting it together, if the chain slips while cranking, valves could smack pistons and cost a lot more to fix.

I don't know if I need a new timing chain or a new tensioner, but I'd like to figure it out before I go any further.

Any thoughts? Anyone else have the head off and experience this?

 

[Froggy]

I hope that you got your engine all sorted out, I had the same problem when I did my 2016 Viper and it was because until you put the head on there is a guide stopper under the head that pushes down on the timing chain between the camshafts which prevents the chain from skipping. According to the Yamaha parts diagram your Venture lite has the same type of set-up. Hopefully this is what is going on.

 

[zigblazer]

It could be that simple. I have not put it together yet. Put off making a decision for too long, but ordered a new tensioner, which is apparently on backorder, due in near the end of the month. There is a guide attached under the valve cover, which could do just what you say, and keep the chain from slipping while cranking. It looks to be in good shape, and I can't find any other reason for the chain to be loose so I'll run with it and hope for the best. Shouldn't be an issue while running, as oil pressure will keep the chain tight then.

Again, I have much experience with larger engines, but never worked on one that was designed to, or had the ability to turn more than 7000 rpm. And I've seen the display show over 12,000 rpm on this. Really crazy for me to think about.