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Discussion Starter #1 (Edited)
Well, after testing and going over every possability I still couldnt decide if my headgaskets were blown. I used a block check kit ( it uses a dye that changes color if combustion gasses are detected in your coolant) negative didnt change colors. Wouldnt over-heat trail riding all day, but would road riding. My engine ice had changed to a purpleish color... but I called the manufactor and they said that was normal because of the dye they used. If I ran the fan overide switch it would stay at 185 deg too with stock radiator. It did have some little black plastick looking peices floating in the coolant. Looked like a radiator hose was deteriorating some. So after second guessing myself I tore my engine down.. Sure enough both heads were blown! Looks like were they milled the heads from the factory it creates small lines that lead right to the coolant pasage. So I have sent my heads and jugs to be ground. I bet I will never have a heating issue or headgasket failure again. I also wasted my money on a PWR radiator. Because I ride with another 840 that has a stock radaitor with a dasa impellor and NEVER has overheated or got close. I wonder how many Teryx's out there are running with a slightly blown gasket and have been updating there coolant system and it is not the real issue. Again this was milled marks from the factory were they cut the heads. I bet there are alot of stock bikes out there with head gasket issues and the owners have no idea. Again there was NO coolant getting into my oil or into my cylinders and both heads were blown. Just a small amount of combustion was passing into my coolant under a load.. Like climbing a huge dune or hill and the temp would start climbing. Let it idle and it would get from 215 to 185:think: All this sounds like a common issue , espeacialy with 840 owners even though I dont think it is isolated to BBK, standard bore with the higher compression has the heating issues too. If I was doing one today I would pay the extra $180 bucks and have my heads ground and jugs right off the bat. Then for sure you wont have this issue.
 

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Discussion Starter #3
Maybe this is the reason the Teryx has had the reputation that the cooling system isnt up to par :confused: I know FST has no problems controling the heat with the stock system yet DASA and everybody else says you got to upgrade you radiator:confused: I would be willing to bet there are alot of blown head gaskets out there and the owners have no idea.
 

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Discussion Starter #5
Also what did you come up with on the front end,that would be good to know. sorry for the hijack. lol
Well the diff project got put on hold after I began this. :D As soon as I get my engine back in good shape I will tackle that one. Also noticed something else. The rear cylinder was running really LEAN. Even though I tuned both. I think the scavaging changes depending on conditions so when I retune I am going to run the rear a little fatter to compensate for this.

Got your PM WVyankee, I will be joining .. Thanks :wave:
 

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I for one have the stock cooling system and don't at least at this time have cooling issues. Hey wildcat we are hoping to come your way this summer on vacation to ride. Possibly Coal Creek. Do you have any suggestions on a vacation worthy destination?
 

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Discussion Starter #7
I for one have the stock cooling system and don't at least at this time have cooling issues. Hey wildcat we are hoping to come your way this summer on vacation to ride. Possibly Coal Creek. Do you have any suggestions on a vacation worthy destination?
Coal Creek is nice so is Brimestone or if you want the appalchian mtn feel Black Mtn. You wont go wrong with any of these places. I would probably recomend Brimestone out of the three .. But you will love any of them.
 

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another way to check if you have blown head gaskets on the teryx which i learned when a had a vforce is to take a spark plug out and use an air compressor and force compressed air down the spark plug hole, if you get bubbles in the radiator you have a blown head gasket.
 

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I have the stock rad. and stock impeller on my FST 840 with no issues runs between 190-215. I also run evans coolant.
 

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I will say this ... since day 1 doing 840 kits. ALOT OF cars that are run in the DUNES, DESERT, 80 to 100 degrees out side and PUSHED HARD .... DRIVEN HARD will overheat. Even cars with oil coolers, impellers, radiators and evans are blowing head gaskets. So what can you do ....

1. make sure surfaces are 100% flat
2. run good gas
3. install a temp gauge ..... once the car gets to 225 SHUT IT DOWN
4. make sure the system is burped and no air in the lines.

i am not saying EVERY 840 will blow head gaskets or that 840's have head gasket issues. Sandjunkie has an FST 840 with ported heads, stock valves and stock carbs ... NO ISSUES with about 2 seasons on it. Speeddemons FST 840 build with ported heads and 38mm throttle bodies NO ISSUES just over 1 season. I can name about 5 others right off the top of my head that HAVE had issues.

So IMO ... IMO ..... do the above 4 things mentioned and WATCH YOUR TEMPS. Get one of our new gauge pods .... this will put the temp gauge RIGHT IN FRONT OF YOU .... if you are not in the sand and not pushing the car hard YOU SHOULD NOT HAVE AN ISSUE. I also feel outside temps play a big role. This is just what i have seen. i have logged a massive amount of dyno time and seat time in alot of 840 builds. The cars that are having head gasket issues .... are PUSHED HARD and DRIVEN.
 

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Discussion Starter #11
Good post Steve. I drive my car hard.. So does Merlin. His head gaskets are fine with 1 1/2 plus valves , massive porting , bored throttle bodies , NOS and with a stock radiator. I think mine were blown from day one. My issue
was the heads. My bike overheated a few times bone stock. Like DASA said " If your heads are not perfectly flat and smooth they will blow" I also think there is something to watching the temps. Dont let it climb. If your heads are in good shape and it is hot 90 to 100 deg watch loading it down for long streches. If your gaskets are blown 20 min of hard riding it will already be pushing 220 deg.

If you are doing a 840 build a light grind on your heads are like $50 bucks each. Good insurance since it blows on the head side.
 

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Old time fix for blown head gaskets

I know this is old school racing stuff you guys already know but I thought I would run it by you. It probably has no use with the new stuff you guys are running but at least I thought I would share it with you. If I had a blown head gasket problem, I would go this way myself.
This may not be pertinent to this tread. But when we had this problem of blown head gaskets when we changed from cast iron to alum blocks and heads. It was identified as gasket creep that was either lifting the gasket or allowing it to move at high pressure, leading to it finally failing. They came up with a fix that I believe is still being used in some areas of racing today. They lightly ping with a center punch, both the heat and the case milled surfaces. They also painted the head gasket with a thin layer of alum paint and allowed it to dry before the torquing procedure. This may seem way out of the box to you, but that was how we overcame blown head gaskets, before they came out with the new generation of triple non blow gasket.
Of course you still want to make sure your torquing sequence is correct as well as using no more then 5# each head bolt at a time.
 

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I'm not sure but do the teryx have torque yeild head bolts. If the do they need to be replaced every time they are used. I know that people that try to reuse them on the yfz are always the first ones to blow a head gasket. Just a thought. Plus lots of lube when torquing them down helps with getting the torque right to.
 

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I know this is old school racing stuff you guys already know but I thought I would run it by you. It probably has no use with the new stuff you guys are running but at least I thought I would share it with you. If I had a blown head gasket problem, I would go this way myself.
This may not be pertinent to this tread. But when we had this problem of blown head gaskets when we changed from cast iron to alum blocks and heads. It was identified as gasket creep that was either lifting the gasket or allowing it to move at high pressure, leading to it finally failing. They came up with a fix that I believe is still being used in some areas of racing today. They lightly ping with a center punch, both the heat and the case milled surfaces. They also painted the head gasket with a thin layer of alum paint and allowed it to dry before the torquing procedure. This may seem way out of the box to you, but that was how we overcame blown head gaskets, before they came out with the new generation of triple non blow gasket.
Of course you still want to make sure your torquing sequence is correct as well as using no more then 5# each head bolt at a time.
WOW!
I haven't heard the Aluminum Paint trick in years!!
We used to do that back in the day along w/ the center punch thing too!
 

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heads

I had sorta the same problem. Mine is just a stock 750 and it kept getting hot and would start smoking like the rings were going bad. I tore it down and replaced all the top end gaskets and put a new piston in ( the rear one was cracked) and new rings and still didnt solve the problem. After i looked a little closed i noticed both of my heads were cracked in exactly the same spot where the oil feed line goes through the head. Any suggestions on what went wrong or how to prevent it from happening again?
 

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Best thing for 840 and bigger is the ARP Head STUDS they make a world of Difference,set them at 42 foot pounds and you are good to go,I have a Drag only Brute 840 FST motor has the new Stage 4 cams and Dasa Racing CNC Ported Heads and ran all season with no issues at all,pulling it down this week to check it all out if I get time.The Studs make a difference,Weller Racing sells them and AMR,Big Kevs Performance,Big Kev sells them on his web site and is quick on shipping.I wouldnt feel safe running stock head bolts on my 840 to much time and money to blow a gasket and be Side Lined!!!!!
 
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