When the mixture is right I often find that the zenith carbs seem to be set nearly at the rich end of the adjustment range. I am wondering if maybe these carbs don't have the right needles and jets. Rob
............................................. ----- Original Message ---- From: Nigel Baker <[EMAIL PROTECTED]> To: [email protected] Sent: Wednesday, 9 July, 2008 2:30:56 PM Subject: Re: [DOG mailing list] RE: Fw: GUD They tell me it is as rich as the needles will go which makes me suspicious. I will get the Carbs and check myself as I think I know what is wrong. When it was overhauled the needles were set as per the book but hey have been playing with it since. Cheers. Nige. ----- Original Message ----- From: Rob Thompson To: [email protected] Sent: Wednesday, July 09, 2008 1:51 PM Subject: Re: [DOG mailing list] RE: Fw: GUD The twin SU carbies are generally zenith brand ...the mixture adjusting tool can be purchased from many of the VW enthusiasts shops for about $25. To do the initial set up on the carbs refer to the Limbach manual. After that I find the best way to fine tune mixture is to go by the spark plug colour - when you adjust the carbs make the same adjustment to each one. The valve seats in Nigel's photos are pretty tragic...the compression and performance must have been noticably on the decline for a while.......running too lean will burn valves and seats (mixture still burning as it leaves the chamber). Also the standard VW seats and valves are prone to corrosion...Nigel tells me the new Limbach alloy valves are anecdotally good. Running stellite seats with standard valves also is much better than standard seats. Don't be tempted to use hard valves with hard stellite seats however as the combination has been reported to fail in some VW motors. Rob PO Box 129, Lawson, NSW, 2783. phone 02 47592307 mobile 0429 493828 ............................................. ----- Original Message ---- From: Sean Jorgensen-Day <[EMAIL PROTECTED]> To: Nigel Baker <[EMAIL PROTECTED]>; DOGS <[email protected]> Sent: Wednesday, 9 July, 2008 10:42:35 AM Subject: [DOG mailing list] RE: Fw: GUD Nige, What options are there to get the thing running richer? Sean -----Original Message----- From: Nigel Baker [mailto:[EMAIL PROTECTED] Sent: Wednesday, 9 July 2008 10:03 AM To: DOGS Cc: Sean Jorgensen-Day; Sean Jorgensen; Russell White; Rob Hanbury; Redmond Quinn; Michael Shirley; Kevin Lewis; Keith Gateley; John Hudson; Harry Bache; graham marsh; Gavin Wrigley; Damien O'Reilly; Colin Turner; Catherine Conway; Baylee Roberts Subject: Fw: Fw: GUD G'day Dogs and others. I have added other Limbach users to this mail for their interest. The attached images are from a L2000 as fitted to the Grob109 which is essentially the same base engine as used in the Dimona. The aircraft had some suspicious damage to the Prop which required a Bulk Strip. The Crank was cracked and a new shortblock engine has been ordered. When we stripped the engine I did not like the look of the Valve seats so sent these images to the factory for comment which is below. Also one valve was noted to be "sticking" when turning the engine over during disassembly. Whenever Peter says something needs to be "controlled" he means "Checked". I rang to clarify a few points. By "Valve Play" he is referring to Tappet Clearance not Valve Stem clearance. By poor carburetion he means "Poor as apposed to Rich" thus he means "Lean Mixture". He has suggested that the corrosion has come from the use of Avgas. He stated that in Europe they normally have trouble with corrosion on engines using Avgas and seldom found on engines running on Unleaded. In the past Peter has said they prefer the engine be run on Unleaded instead of Avgas. Avgas 100LL of course is still acceptable. This is of course 98oct unleaded so Premium Unleaded. This must be the 98oct variety and not the 95oct. I use BP Ultimate. Of course I have a problem looming. The eastern states are now requiring 10% Alcohol content in car fuel and expect that will spread through all states. I understand the US is in the same position and much of Europe. The Limbach Engine is rated for 5% Alcohol and the last time I discussed this with Peter (a while ago now) he said they would be changing it to 10% or higher. Brazil's fuel spec for instance is much higher being over 20%. While my fuel hoses are rated for Alcohol I still have the FRP fuel tank which I believe is not. So changing to the Alloy tank is pending for me. That leaves the Fuel Cock and Electric Fuel Pump left in the circuit to worry about. The seals I put in the Fuel Cock are OK with Alcohol but will have to check up on the Pump. Something for you all to ponder if running unleaded like myself. Below is the correspondence as mentioned. Cheers. Nige. ----- Original Message ----- From: "Peter Salomon" <[EMAIL PROTECTED]> To: "Nigel Baker" <[EMAIL PROTECTED]> Sent: Friday, July 04, 2008 7:30 PM Subject: Re: Fw: GUD > Nigel Baker schrieb: >> G'Day Peter. >> Attached photo's of the Cylinder heads off the engine that had the Shock >> Load. >> Can you give me an opinion on the corosion to the Valve Seats. >> This aircraft was being flown every month but the Airfeild is near the >> Ocean. The climate here though is not humid. >> There is also a grey/white powder over the surfaces of the intake ports >> and cobustion chamber. >> Any ideas of why it is this bad. It is 48 hours since overhaul. >> Regs. >> Nigel. >> > Hi Nigel, > > blimey, what type of fuel fly your client? > After your pictures can I find some problems with the heads. > 1.) I think the left head on your picture is from the right engine site. > I can see that the exhaust valve from cylinder no 2 have burn tracks. > No valve play! > Slight leaky between cylinder and head. > Overheating failing could be poor carburation! > The corrosion on the seats could come from using AVGAS! > The beading in the ports show me very high exhaust temperature! > On cylinder one the intake valve have also burn tracks outside. > Please control this valve. No valve play could be the reason. > > A new (complete) engine will help. ;-) > > Best regards and nice weekend. > > Peter > > --------------------------------------------------------------------- You are subscribed to the Dimona Owners Group mailing list. 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