I lost my muffler of a Surpass 91 today...the thead in the head was worn and no amount of tinkering would fix it. I even put in a grub screw to try and secure it but no luck. It ran fine without the exhaust and another guy at the field said he ran a four stroke for 2 years without a muffler with no problems. Any comments would be appreciated as my last option is to get a cylinder head and new muffler which is expensive. The engine is in a 4 star 60 so there are no venting problems to overcome as the engine has no cowl. Thanks.

Giday mate I,m in sth Island Rangiora anyway easyway to fix your prob is to get a heli coil you screw it in and it replaces the thread thats stuffed if you are worried about doing it yourself most small eng shops can do it only takes about 20mins to do youhave to get helicoil to the size you wish to end up with hope this helps my question to you is how do you post questions on this forum (radios)
I,m at prrj@xtra thanks Paul

Clarence Lee can put a bushing in your head to replace the worn out threads.

Lee, Clarence F.
10112 Woodward Ave
Sunland, CA 91040-3342
(818) 353-7356

Hope the Kiwis don't mind me jumping in to the middle of your conversations!

Regarding the original question, 4-stroke engines are a lot less critical as to the need for a muffler and maintining a specific exhaust back pressure than are 2-strokes, so it's not surprising that you and your mate have been able to run well without any muffler. Helicoil is an appropriate solution, and if you have a good race engine shop in the area (I know that there's some, since my wife and I have been to one of the Saturday night short track races on the north island down there!) they can probably do this for you or recommend someone else that can.

As to how to start a new thread, go to the main page of the section on which you want to make the post and click on "New Post" in upper left area and go from there.

Beautiful country with a very interesting history you have, just wish that we had been there longer and also that we had also gone to the south island.

I've had a couple of engines fixed by Clarence Lee. Great fix. Cost $28.50. Send head with exhaust pipe (if you have it) to Mr. Lee with check or money order and you will have your head back in less than a week. Cheaper than a new head.

Cheers,

Chip