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Old 09-25-2008, 06:40 PM
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Skyventures
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I have a Jett 60L and the head bolts keep coming loose. I have tightened the bolts in a cross pattern many times and now probably need new bolts. I am also having problems with burning out glow plugs. I have tried OS #8 short and long plugs, and R5 and Fox long with idle bar. I am using XPFuel, Syn Xtreme 15 (Oil content - 18%, Nitro - 18%). I also would like to purchase the Merlin and K&B long reach idle glow plugs, but the dealers near me up hear in Alberta Canada don't carry them. Where am I able to order these glow plugs?
Any suggestions would be greatly appreciated.
Doug
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Old 09-26-2008, 07:52 AM
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ORIGINAL: Skyventures

I have a Jett 60L and the head bolts keep coming loose. I have tightened the bolts in a cross pattern many times and now probably need new bolts. I am also having problems with burning out glow plugs. I have tried OS #8 short and long plugs, and R5 and Fox long with idle bar. I am using XPFuel, Syn Xtreme 15 (Oil content - 18%, Nitro - 18%). I also would like to purchase the Merlin and K&B long reach idle glow plugs, but the dealers near me up hear in Alberta Canada don't carry them. Where am I able to order these glow plugs?
Any suggestions would be greatly appreciated.
Doug
Hi Doug......

Do you have a regular SJ-60L or the 60LX engine ?? Do you recall when it was purchased?

The head bolts will come loose if the engine gets lean and overheats. We have seen this happen many times, and the bolts coming out is an indication that the engine got extremely hot during some portion of a flight. Glow plugs blow 95% of the time because of a lean run. So use this as a cue to look into a possible problem.

The difference in expansion rates between the aluminum crankcase and the steel bolts is what does that. It happens more often on the BSE engines, but we do see it now and then on the cast case engines too.

Always set the engine high speed mixture 600-800 rpm down from ground peak rpm for flight. On the 60LX we sometimes back off as much as 1000 rpm. The engine needs the extra fuel when it stages on the muffler in flight. Find peak briefly, and back off from there.

Make sure your fuel system is perfect - the tank must be isolated from the fuselage with foam rubber or you will develop fuel foam when the engine unloads in flight (and it will go lean and get hot in flight). If you are already using a bubble-jett or tetra fuel tank, the foam would not be an issue, but check the other fuel tubes too.

Glow plugs.......
It is not blowing the plugs because of the type or brand of plug. Its getting way lean at some point during flight.

The engine likes a hot glow plug. Lots out ther there to choose from.
The following work well.....

OS A3, Enya 3, Rossi 2 or 3, McCoy 59, K&B1-L, K&B-HP, Fireball Hot,
Fox Std Long, Hangar 9 #3 performance plugs, hangar 9 2c super plug (and the H9 sport plugs work ok too).

You can use the OS#8 usually, but we have found that engine transition and idle is not as good - plug is a bit too cold.

The Merlin HD hot plugs are available from Jett and direct from Merlin.

Also, these have also proven to work pretty well....
hangar 9 4c super plug, OS type F

Do Not use idle-bar type glow plugs.

Two key things you have to do:
1) check the fuel system and fuel tank installation
2) Tighten the head bolts. Put the engine back on a test bench. Run it there. That is the only place you can diagnose an engine issue. Warm it up, find peak rpm, back off 500 rpm - run it there. Check throttle and transition. When you shut it down, let it cool a minute and then re-tighten the head bolts. Check to see if the glow plug is intact.

If it runs properly and does not get hot or blow a plug on the test bench, you know the issue resides in the airframe.

If it does not run properly (needs to get up to at least 17,500 rpm on a 10x6 or 9x8 prop at peak, and stable down 500 rpm from that peak) get back with me.

Let me know how you make out

Bob
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