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MowerMan
MowerMan, Small Engine Technician
Category: Small Engine
Satisfied Customers: 39
Experience:  20+ years experience rebuilding small engines. Specialise in vertical crank mower engines.
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have a v twin Briggs and stratton on a costume made trike.

Customer Question

have a v twin Briggs and stratton on a costume made trike. It has a mikuni carb and a turbo off a Masada engine. It smokes allot but I know it is running to rich,but my problem is it wont ideal after the engine worms up. It ideals good when it is cold. do you have any suggestion's?XXX@XXXXXX.XXX thank you.
Submitted: 5 years ago.
Category: Small Engine
Expert:  MowerMan replied 5 years ago.

Hi - Phil here. That's right up my street - A B&S with a turbo - WOW!

 

OK some preliminary questions - are you using the turbo in draw-through or push-through mode - IE is the turbo pushing air only, or fuel and air?

 

What's the boost pressure?

 

What RPM are you getting?

 

Boosted engines have different carb requirements from the normally aspirated versions.

 

You won't pay anythng until you ACCEPT an answer. You must place a deposit on file to READ an answer - then you can decide to accept or not.

 

 

 

Customer: replied 5 years ago.
graphicgraphicgraphicI bought the trike the way it is,so I don,t know allot about how the turbo works. The gage reeds 10lb on vacuum side at idle. don't have a tach, but it wont idle after the engine worms up.I took pictures but don't know how to send them.the carburetor is a mikuni with the square slide with only one adjustment screw. I know it is running way to rich,because of the way it smokes. the engine only has about 50 hrs on it. If I need to rejet the carb would I go bigger or smaller jets? The turbo came off of a Masda and on a V twin briggs & straton 18 hp. need to get engine to idle so the clutch wont stay in gaged.graphic
Expert:  The Home Smithy replied 5 years ago.

HiCustomer

Mowerman is off line at the moment as he resides in the UK. Just thought you would like to know that it may be a while till he is back on the site. It would also help if you could back away from the trike and take the pictures again. They are too blurry at that close a distance.

By the way it sounds like a SWEET set up!

Best, THS

Customer: replied 5 years ago.
my camera isn't that great. It looks like you can see the turbo. but I don't know if the turbo wood have anythig to do with the idol
Expert:  The Home Smithy replied 5 years ago.

Kickstand, the camera is ok. And yes the turbo has a big effect on the carburwators ability to idle. But that subject needs to be addressed to Mower Man. He is the turbo guy. Not me. I am just helping him out by seeing if you could get a clearer shot is all. The cameras in phones are no good close up. Just pull away about 2 or 3 feet. The picture can be enlarged to see the details after that The first picture came through all stretched out. Cant even tell what it is.

 

BTW the fee to solve your problem is one time only. You click on "I accept the answer" only when the question has been answered to your satisfaction.

 

Please get a couple more shots for us. It would be helpfull. That and I would love to see the trike too.

Expert:  MowerMan replied 5 years ago.

Hi, - 'Smithy' is correct - the turbo will have an effect on the carb's ability to provide the correct mixture. From your pictures it looks lke the turbo is pullng through the carb. This is the easiest method for low to medium power applications.

 

Your engine is being over-fuelled - more noticable at idle, but almost certainly it will be rich at all speeds and power levels. This is always a danger when matng engines and turbos that were never designed to work together.

 

Don't know how far into the workings you want to get, but to make this perform properly, some calculations will need to be done regardng throughput, and for that you will need to know what power level and RPM you are aiming at. Then the correct jet sizes can be calculated, which may or may not be 'do-able' with the carb as fitted.

 

I appreciate that you bought this mean machine 'as-is', but do you happen to know what the capacity of the 'donor' engine was? Something around 700CC would be great.

 

I suspect that your engine is being 'over-boosted' - if you ae reading 10 PSI boost at idle, this is confirmed. In essance, the turbo is boosting and and trying to make the engine accelerate but you are holding it back with the throttle. Is the turbo fitted with a waste gate?

 

There are 2 ways to solve this - basically adjust the boost to match the engine's requirements (which is the function of a wastegate), or re-jet the carb (smaller jets) to compensate. If you go for re-jetting, this MAY result in a lean mixture at full throttle - particularly as there only appears to be one adjustment screw.

 

MowerMan, Small Engine Technician
Category: Small Engine
Satisfied Customers: 39
Experience: 20+ years experience rebuilding small engines. Specialise in vertical crank mower engines.
MowerMan and 2 other Small Engine Specialists are ready to help you
Customer: replied 5 years ago.
graphicgraphicgraphic
Customer: replied 5 years ago.
graphicgraphic
Expert:  The Home Smithy replied 5 years ago.

Hey, Now that is SWEET!!

Or to use a more British term; That is the dogs bollix

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