I have purchased a Irvine 53 but after running it in I now have some trouble getting it to run perfect.
It can run OK for several minutes, responding perfect, but suddenly it stops throttle OK, it just wont go to full speed. I then have to adjust the fuel needle to give it some more fuel. Then it throttles to full speed again and I can then adjust the needle back to where I want it at full speed, now it runs perfect again ,but suddenly the throttling gets bad again.

Since the engine in periods runs OK I don't want to adjust the acceleration screw because I the will get other problems instead.

Anyone out there who have experienced the same problems or have any tips ?

PS. I hope you can understand my English, its difficult to get all technical words right....

Check your low speed needle. It should be about flush with the brass housing it is in. I have had mine creep in due to vibration and It would run poorly, kind of what you are describing

Thanks for your reply !

I will check the lowspeed needle when I return home. But still I think its a little strange that it can run OK for several minutes and then suddenly refuse to throttle from low to high speed, can it maybe have something to do with the temprature of the engine ?

I believe your large needle valve is too far in.
Loosen your high speed needle valve like you say you did...then leave it. Your engine will run slightly slower but will have enough extra fuel to keep the engine cool. When you reduce the fuel, it runs faster, but then overheats.

From your desrciption the problem could be fuel foaming. If you're riching the high speed needle a full turn or more to get the engine to settle down that would be my guess. Use a balancer to get the prop in perfect balance.

Also watch the fuel line and you may see it turning foamy looking.

I did not even notice that my Irvine 53 has a needle valve! That thing is "Automatic".

I might just JB weld the needle where it is, since it is the best engine I HAVE EVER RUN...

Keep us posted,
jimmer

my irvine did nearly the same thing found some very small trash in the needle valve (thats when i learned you should use a filter on ANY engine)

The only two times my Irvine .53 ran poorly was when I lost muffler pressure to the tank. First time the pressure fitting came out of the muffler and fell "somewhere" and the second time I forgot to connect the line after I had fueled.

BTW if you ever lose your muffler pressure fitting it appears to have metric threads. If you can't find a metric tap, chase the threads in the muffler with an 8x32 tap and insert an 8-32 pressure fitting using some loctite.

My experience.

Dan