I was given a Magnum .40 for my new airplane. It seems powerful and I like it. But the engine blows fuel oil everywhere. By the front crank opening, out of the carb. The low idle could be better and it somtimes dies on me in the air.

Any suggestions for fixing? I thought about pulling it a part and give it a good cleaning.

Your thoughts are appreciated.

Tim[]

You should move your question over to the engine forum. You will probally get lots more answers from some really good engine guys there. Jeff

YOu mean the front crank opening where the bearing is located? If so I'd say your front bearing has gone bad.. It's not sealing any more.. Idealy there should be NO or VERY little oil coming from there.. When I say very little I mean hardly noticable.. I don't know about the carb issues though!

Is it mounted upright or inverted.. What do you mean low idle could be better? Is it loading up on you then sputtering when you try to go Full throttle.. or is it just slowly revving up?

I don't believe I've ever had one shoot out oil from the carb!

What fuel/prop are you running?

Ice,

I'm using cool power 15% for fuel. The engine doesn't like to idle. The high speed is tweak to max RPM when I hold the airplane vertical and then I tweak it back a little to keep the engine cool. You will see a small smoke trail when you throttle up. So I think I got that side set up well. It's the low side that is giving me trouble. It spits fuel right back out of the carb which should be an indication that the low side is to rich. ( I think) So I try to lean that out a little and it just dies. I'm going to tear it down and give a good cleaning, replace any bad seals or gaskets.
But you thought of the bearing being shoot has me agreeing with you. I noticed I have extra play allowing the crank shaft to slide in/out of the crank case. I will check the bearing and replace.

Thanks for your thoughts,
Tim

Which Magnum do you have?

They made a GP 40 with no ball bearings and a air bleed carb.

There was a PRO 40 with ball bearings and a twin needle carb,

Then there was the XL 40 with ball bearings and a twin needle carb.

Enjoy,

Jim

Jim,

It's a GP40. I just pulled it apart so I could clean it. I only see the crank cover gasket and the carb o-ring that should be replaced. Over all it looks good inside. Only the external fins on the head are gummed up. But I did notice the head bolts were'nt all tight.

Hopefully giving it a good bath and torquing the engine bolts correctly it should be fine. But I don't understand the fuel spitting out the front through the crankshaft bushing.

I need a beer to think this one over.

cheers,

Here are the brgs that go on these Magnum's
Model PRO R6 & MR6902 - rear & front respectively
Model XL MR607 & MR6902
Model XLS MR6902 & MR6900
all brgs are shielded.

The GP 40 has a bronze bushing for a bearing.

The engine is no longer made.

There were other engine made that were excatly the same engine... Tower 40, Thunder Tiger GP40, and the Magnum GP40. The OS FP40 was the same except around the carb area.

There's nothing about the current Thunder Tiger GP42 that will interchange.

The Magnum GP40 was made by Thunder Tiger.

Bushing engines sometimes are a little messy around the front of the bearing. Its better for them to be this way than to not have oil and wear out.

An engine running rich has more tendacy to be sloppy on the outside.

All our glow engines spray a little fuel out of the carb when running, especially when run rich.

Your engine should be fine.

Enjoy,

Jim

Jim

Looking for bearings specs ( dimensions ) that go on the Magnum GP 65 SE ?

Sorry to use this thread - which forum to use for these type of ques?

Thanks

This is the area where you ask these questions. You are doing OK.

If you have a question, you should ask it as a "NEW POST" rather than as a "REPLY" to someones else's post.

To my knowledge, the GP 65 was a bushing engine but I've never actually seen one.

Enjoy,

Jim

Hi!
Having an engine that leaks fuel out through the front bearing is something you have to live with occasionally as it depends on the crankshaft to engine housing fit...not to if the ballbearing is bad or if it is shielded or not. That is a misconception among many modelers.

My advise to you is to use a milder fuel...let's say 5%nitro and 20% castor oil(or a mix of castor and synthetic oil).
There are some engines that can't tolerate as much nitro as 15% nitro as their combustion chamber is to small (they have too high compression built in). Symptoms using too much nitro is very finicky high speed needle settings and engine could abruptly stop at high or low throttle settings.
A suitable prop is a 11x5 or 11x6 APC (if you fly at sea level) Not a 10x6!
And a suitable glowplug is an Enya 3 or OS 8 glowplug.

Regards!
Jan K
Sweden

I gave the engine a good cleaning. I mic'ed the crankshaft and the crankshaft bushing (no bearings), and I got about .003-.005 clearance. Which I think is fair for a used engine. So I think I'll try a lower nitro and see what happens. So this weekend will be in the backyard tuning the carb. Wish me luck and I try to keep all my fingers.

cheers,

Tim

p.s. thanks everybody for your suggestions. I love this website.

This is the engine forum



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