I have an Evolution 58 and up until recently it was a real screamer. I have read all the threads in here pertaining to it and I still have a few questions hopefully you guys can help me with. Last year it flew with no problems whatsover and this year its nothing but problems. I replumbed it with new tygon this year and have repeatedly inspected the fuel lines with no problems found. It keeps dying in flight even after running a whole tank on the ground with no problems. I have looked for the head gasket issue and at first inspection I see no evidence of that, but I have yet to disassemble it. It still has compression so I don't see rings being an issue. The only thing I have yet to really look into is the ignition. It seems to work fine but I had a local hobby guy who really knows his stuff (sponsored by BVM) said that it had problems with that ignition running at 4.8 V and solved dying issues by running it with regulated 6.0 V power. I spoke with Horizon and they said that it would run fine on 6.0 V but didn't know if it would fix my issues. Its getting real frustrating as I don't know what else could cause this and I am tired of having to to dead stick every flight (some not ending so well and my TOC Yak is really taking a beating ). PLEASE HELP ME!!!!

Tough enough to diagnose my own problems up close, let alone yours at a distance.......Have you tried a peak-hold temp sensor (Venom makes one) to see if overheating is a problem. Pe Reivers suggests an occasional drop of oil on the front seal, maybe that's leaking. The fact it does it in the air suggests cowl pressure, maybe try a line into the fuse if you don't already have one. Perhaps revisit the tank lines, I have had leaks after I replaced Tygon......Did you clean the carb screen? I like to kit mine.
Just some suggestions, I know your pain. Good luck.

yeah I have the line already ran into the fuse. I did disresmeble the engine and found that the head gasket was in fact blown . It was missing a chunk about 1/4 inch in length. What kinda of symptoms would you see in this scenario. Does it sound like my problems could be stemming from that or should I continue to look further into this issue. One other thing I forgot to mention is that it is EXTREMLY difficult to start.

If the piston/jug looks good, I would replace the bearings, seal, and gaskets. The older Evolutions had smooth surfaces that led to gasket failure, rough them up if that's what you have. Blown gasket would certainly cause issues.

The broken gasket probably is the cause, together with carb reference pressure. It does cause the engine's difficult starting for sure.
Line in the fuse is not the solution. Use static tube or static port systems.

Static ports/tube? Can you point me in the right direction on that....not familiar. I did change the gasket last night....smooth surfaces. I didn't rough anything up but I did use a little of that permatex copper coat stuff.

you should have roughened up the surface.
do a search here on this forum for static tube or static port.
Also read the article I wrote here:
http://prme.nl/forum/viewtopic.php?t=205

Yeah I will rough it up on the next rebuild (which hopefully doesn't come for a while). This engine is on a Yak 54 and I noticed you mentioned several times about putting on a straight part of the fuse. Since its round there is no "straight" lines but are you basically saying to find a laminar area of air flow like perhaps a few inches ahead of the wing or right infront of the the windscreen? Also would you consider putting a carb cover over the throat of the the carb? Lastly, I am an Airline pilot so I am reasonally familiar with Pitot/Static systems (just not on models) but all static ports I have seen are small disks with 1-3 pinholes in it flush mounted somewhere mid way down the fuse. Would something like this be a better option (machined out of aluminum or other) or is the tube out in the airflow with the holes in it just as affective. Again thanks for the help with this.

[QUOTE=westwind1124;1532772] Lastly, I am an Airline pilot so I am reasonally familiar with Pitot/Static systems (just not on models) but all static ports I have seen are small disks with 1-3 pinholes in it flush mounted somewhere mid way down the fuse. QUOTE]

Hi, then you problably have noticed that there is static ports at both side of the plane and in many cases 4 of them (separate systems left right side), and that they are connected to each other 1 left+1 right to system 1 and so on that you can get proper measuring. And everytime you do your preflight check and look at the pitot tube you problably also look at a static port, depends a little of aircraft of course.
/Lennart

Yes this true, but I don't think I will be installing four static ports on a 50cc yak . Ok here is a pic of what I did. Would you please confirm that this is sufficient or should I reengineer anything.

Prolly just fine. I've been told to use a T with one on each side due to pressure differential in Knife edge. Haven't ever done it.

I have an engine tightly cowled in, front carb which was impossible to tune due to extremely rich midrange.
Adding the static tube allowed the engine to be tuned in 5 minutes with smooth running static and in flight.

@ Westwin1124:
With straight I mean in air flow direction, not fuse cross section. That is why in front of the wind screen is not a good idea, because the airflow is not in straight lines there.
In fact, the static tube is a tube with static ports in it. If we need reference pressure only, flush ports can be directly on the fuselage. For high alpha flight it may be needed to place several ports and connect them to a small plenum chamber close to the carb, so the pressure in that chamber is the mean value of all ports.

We have this with 2 0.8mm holes, but I will also test the "normal" flush" one at each side.
/Lennart

Ok so should I put one on the other side then since it is a a 3d aircraft and will be seeing some odd flight envelopes. Can I just tee in the middle between the two