5 year rubber replacements after motor runs crappy

[Byron]

see video:

 

 

Hello everyone,

 

I recently purchased a Drifter with 200 original hours on the motor. Owner didn't do complete much heavy maintenance but changed oil, plugs, filter, ect.

 

Last month I installed a new rotax oil filter, new fuel filter custom fuel lines. Oil Changed, coolant changed, and "choke" cable system replaced. Minimum throttle idle speed is too low. I need to purge the air from the oil lines I recently became aware of.

 

Parts were ordered from the aircraft manufacturer. The fuel lines were made from experienced aviation tubing manufacturer who is very familiar with rotax engines.

 

Pertaining to the video....The first signal I'm showing in the video is 2000rpm. The second signal I'm showing is the mixture control. I Decrease "choke" or enricher lever and have power loss. First time today I heard a power oscillation at 3000 rpm.

 

Motor doesn't sound aweful, but isn't quite right. I want this engine to purr like a kitten. I think it can.

 

Comments, analysis, tips, suggestions are welcome. THAT'S WHY I POSTING THIS. Maybe it can help someone else in the future.

 

Fire away

 

 

[Byron]

I fogot to mention...opened up the carburators and changed the gaskets on the float chambers, chokes, and diaphrams and fuel pump.

 

 

[skeptic36]

Are the carb mount rubbers in good condition?

 

 

[Byron]

I'll check in the morning, but that wouldn't affect it needing full choke to run smooth and not loose rpm. Right?

 

 

[skeptic36]

If it's sucking air downstream of the carbs, that leans the mixture, applying choke enriches the mixture.

 

Seems likely to me, but I'm not a mechanic

 

 

[facthunter]

The choke is only effective when the throttle is near closed on that type of carburettor. Have the compressions been checked? Nev

 

 

[Byron]

Yes, I'm aware of the throttle position during start up. I watched Phil Lockwood speak about Rotax 9 series on YouTube.

 

https://www.youtube.com/watch?v=TMXYWDxjccg

 

Something happened replacing the parts I mentioned. The motor was running great before the 5 year rubber replacement. Only 200 hours on the motor but its 10 years old.

 

 

[Byron]

If it's sucking air downstream of the carbs, that leans the mixture, applying choke enriches the mixture.Seems likely to me, but I'm not a mechanic

Interesting idea. It seems plausible. But 4 months ago, before all the new parts mentioned were replaced. The engine sounded beautifully. I will definitely check the carb mount rubbers in a few hours when the sun rises.

 

 

[ruffasguts]

Possible that the distribution spider eg the splitter to the carbies and return line has been incorrectly fitted. The return line /pressure gauge fitting has a restrictor in the fitting. If installed in a carby supply line one carb is starved of fuel. An easy error to make if not known

 

Mick W

 

 

[crashley]

have you rebalanced the carbies with a vacuum gauge if they are out of balance it will run rough and what do you mean by you will have to purge the oil system the only time it needs to purged is when the engine is first installed . and have you checked for proper fuel flow through the new fuel lines and filter ie disconnect at the carby and measure the actual fuel flow

 

 

[Byron]

 

Possible that the distribution spider eg the splitter to the carbies and return line has been incorrectly fitted. The return line /pressure gauge fitting has a restrictor in the fitting. If installed in a carby supply line one carb is starved of fuel. An easy error to make if not knownMick W

I double tripple checked the fuel line assembly mick, looks all correct. This system doesn't have a return line. Here are some pics

 

 

 

 

[Byron]

have you rebalanced the carbies with a vacuum gauge if they are out of balance it will run rough and what do you mean by you will have to purge the oil system the only time it needs to purged is when the engine is first installed . and have you checked for proper fuel flow through the new fuel lines and filter ie disconnect at the carby and measure the actual fuel flow

Rebalancing is a suspicion of mine also, but would get that rough if I changed the carb diaphragm and gaskets in the float bowls and chokes. Fuel pressure test might be revealing I agree.

 

 

[Byron]

and what do you mean by you will have to purge the oil system the only time it needs to purged is when the engine is first installed .

I had all the oil lines off and the system was open during the oil hose change.

 

http://www.flyrotax.com/portaldata/5/dokus/d05199.pdf

 

SERVICE INSTRUCTION

 

PURGING OF LUBRICATION SYSTEM

 

FOR ROTAX® ENGINE TYPE 912 i, 912 AND 914 (SERIES) SI-912 i-004 SI-912-018R1 SI-914-020R1

 

1.5) Compliance

 

These inspections have to be performed

 

- before first engine run,

 

- after re-installation (e.g. after overhaul),

 

- after lubrication system opened or drained during maintenance work (e.g. removal of oil pump, oil cooler or suction line).

 

 

[Blueadventures]

[ATTACH=full]42403[/ATTACH] [ATTACH=full]42404[/ATTACH] [ATTACH=full]42405[/ATTACH]I double tripple checked the fuel line assembly mick, looks all correct. This system doesn't have a return line. Here are some pics

Hi Byron

It looks like your carby overflow hoses are longer than usual / specified. Is that the length you have been flying with? I'm no expert so my comment is only that you should check with rotax manuals or a rotax service tech. Are you also checking on the Rotax Owner forum threads?

 

Cheers

 

Mike

 

 

[Byron]

Can you send me a link to the required length of the carb float vent line. I just looked through the installation manual and it just discussed diameter of tubing and avoid placing the end of the tube in a slip stream.

 

Requirements on the drainage piping:

 

NOTICE With closed or blocked leakage piping, fuel could end ƽWARNUNG

 

up on exhaust system. RISK OF FIRE!

 

- The lines have to be routed such that in case of damage the surplus

 

fuel is drained off suitably.

 

- Route the lines without kinks and avoid tight bends.

 

- Route the lines with a continuous decline.

 

- The lines have to be protected against any kind of blockage e.g. by for-

 

mation of ice.

 

venting lines Float chamber venting lines (1): Float chamber

 

Connecting nip- ple for leakage line

 

NOTICE The float chamber venting lines (1) have to be routed

 

into a ram-air and vacuum free zone or into the airbox, according to the requirements and release of BRP-Powertrain.

 

See chapter “air intake system“. These lines must not be routed into the slipstream or down the firewall.

 

Pressure differences between intake pressure and pressure in the carburetor chambers may lead to engine malfunction due to incorrect fuel supply.

 

Connecting nipple (3) for leakage line:

 

-Outside dia. 6 mm (1/4‘‘‘)

 

-Slip on length Max. 17 mm (11/16‘‘)

 

 

[Byron]

Screenshot of the installation manual regarding routing the carb vent line

 

 

[Byron]

Needing full choke for the engine to run without roughness or power loss is a new problem since the installation of the new parts. That is what is so strange. I think a fuel pressure test and good balancing is a start. I just thought maybe it could be a simple fix since it was running great before. Definitely seems to be a fuel starvation problem.

 

Anymore thoughts or suggestions?

 

 

[Byron]

Well here is an update: I looked in the oil reservoir this morning and found my worst fear. White cream on the bottom of the lid. Looks like a blown head gasket:crying:

 

I'm licking my wounds and looking for a head gasket set. If anyone has a link to purchase one let me know.

 

Don't know how this happened. You may send your condolences

 

 

[rick morawski]

Well here is an update: I looked in the oil reservoir this morning and found my worst fear. White cream on the bottom of the lid. Looks like a blown head gasket:crying:I'm licking my wounds and looking for a head gasket set. If anyone has a link to purchase one let me know.

Don't know how this happened. You may send your condolences

I wouldn't jump too hastily to that conclusion. If you have only been running your motor for short periods for test runs then then you will not completely boil out the water in the oil, which will then condense in the oil tank.

Rubber carb sockets should have been replaced at the 5 year rubber replacement. I would check the chokes levers are completely returning to their stops when choke off and do a pneumatic balance of carbs. Spark plug caps on correctly? Both ignitions on and working? Main jets partial blockage with old fuel varnish can be hard to see without magnification (if you are old like me) Those are some things I would look at before ripping the heads off.

 

Cheers

 

Rick

 

 

[facthunter]

Check if you radiator is pressurising rapidly before removing heads. If there is water in a cylinder the condition of the plugs will show it. It all gets pretty clean. Nev

 

 

[skeptic36]

Isn't it only the heads that are water cooled,on a 912, if so why would a blown head gasket allow water into the oil, or pressurise the radiator?

 

 

[crashley]

blown head gasket wont let water into the oil only a cracked head can, but that is extremely rare, more likely condensation in the oil

 

If you are worried about air in the oil circuit you must purge the oil system by pressurising the oil tank with air BEFORE YOU RUN THE ENGINE and I would also check the valve lifters for correct operation as per the rotax manual

 

it may be running rough because of a soft or faulty lifter

 

you must check the actual fuel flow at to each carby if you have played with the fuel system ie if you have changed lines or filter type etc it only takes a bit of debris etc to block a banjo type fitting

 

and the carby balance must be checked as it does not have to be far out to make the engine run very roughly

 

 

[Vev]

You will see condensation react with the zinc in the lubricant if the engine is run for a short period of time and not getting to its normal operating temp for 45-60 min ... This will appear as a cream on the oil tank cap and neck.

 

It does mean you will have a reduction in anti-wear protection, it will also accelerate oxidation of the lubricant.

 

If this is the case, don't be overly alarmed but just change the lubricant and clean up the emulsified zinc and try to avoid short low temp runs, albeit you have other engine issues sort out.

 

As a suggestion to your engine issues, you may want to consider ensuring your idle system is clear of any old fuel residue, which will mean a detailed demantling and inspection of all jets, mixture screws and air and fuel way galeries.... I have seen the symptom of where engines will only run at low engine (>1500 - 2000 rpm) with only the choke on.

 

Others may be able to expand on a cleaning procedure.

 

Good luck ... Hope you find the problem.

 

Cheers

 

Vev

 

 

[gregrobertson]

Just a thought. have the new carbie diaphragms been fitted correctly. there are small lugs on the diaphragms which must be mated with corresponding detents in the piston and carbie body. If they are not lined up the engine will run very rough. Also check that the piston is free to travel up and down smoothly, if the top of the chamber is not tightened correctly it can jamb the piston. Greg.

 

 

[Byron]

Just a thought. have the new carbie diaphragms been fitted correctly. there are small lugs on the diaphragms which must be mated with corresponding detents in the piston and carbie body. If they are not lined up the engine will run very rough. Also check that the piston is free to travel up and down smoothly, if the top of the chamber is not tightened correctly it can jamb the piston. Greg.

I have double triple checked the diaphragm and the are seated great and the dimple is lined up. Checked the piston too. Very smooth...there is a green color one the need tip about 1/2 covering the tip.

 

I will digest the other received comments too. Good stuff