Briggs 3.5 Flathead 91202 - chopper style frame

[g_rashid]

Hey OldMiniBikes!,

I just acquired a DIY chopper build from some guy off of CL locally. It has a 3.5 Briggs. It's a lil rough to the eye but I'd like to get it fired up so it will run smooth .

It was very dirty with lots of grime and varnish in the tank/carb. It would fire but shut off after 10 sec. I completely broke down the carb and cleaned it with gumout. The diaphragm was in tact so I cleaned it and the spring inside as well. The oil was black like soot so I changed it and flushed it out with some cheap oil. I then, filled it with 10W30 synethetic they have on sale at O'reilley's. I didn't want to go inside of the engine because I don't really know what I'm doing.And yes, I will replace the old Champion RJ16LM plug with an E3.10 (preferred) or an NGK BR2LM today or this week, depending on who has it in stock.

Is it possible someone can offer some advise as to what I can do to get it running :shrug: ? Thanks in advance guys/gals.

Peace

 

[07Motorboy]

All the things you did to it should make it run good (especially the carb clean). Also, to cleaned the tank? You may end up needing to adjust the carb if it does not run or run well.

 

[Sinner70]

I'd add a longer exhaust pipe or even a muffler. That one is on the short side (burnt valve).
I'd also add an air filter. You went through and cleaned the carb, you dont want it to get all messed up again. You might have to adjust the idle, it could be on the low side.
Everything else sounds good.
cool frame by the way.

 

[creia]

"... the diaphragm was INTACT so I cleaned it..." (emphasis added)
While it may be "intact" (i.e., no tear or holes) they can get real stiff with age and/or from non-use. To work properly they need to be very flexible/pliable. Try installing a brand new OEM Briggs diaphragm (NOT an "aftermarket" one).
Michael

 

[Outlaw Ace]

"... the diaphragm was INTACT so I cleaned it..." (emphasis added)
While it may be "intact" (i.e., no tear or holes) they can get real stiff with age and/or from non-use. To work properly they need to be very flexible/pliable. Try installing a brand new OEM Briggs diaphragm (NOT an "aftermarket" one).
Michael

Good advice, a diaphragm need to be new or close to it to work properly and the aftermarket ones are not very good in my experience. Those are good engines but the carbs can be terrible to get tuned unless you completely go through them which is not as easy as it sounds, you have to make sure the passages are clear and clean or they will not work right. That's a cool little chopper, you do need a longer exhaust but do not go too long or you lose some power. I put tailpipes on mufflers for the looks and to carry the soot away from the paint. If it were my chopper I'd make a springer seat for it to get me off the ground and for comfort while riding.

 

[g_rashid]

Yeah fellas thanks,

The diaphram was newer. I found out that the idle screw was missing. I put my finger over the hole, started it and it fired. I slid a (non fitting) screw in it ans it stayed running.

Question - Can I install a "regular" screw into the hole to keep it running (I don't want to order anything)? :surrender:

What is the size and pitch of the hole? I'm sure everything (or most) is all SAE instead of metric (OHV/Animal/World Formula engines). It will be impossible to take the carb to Home Depot and measure it.

I don't weld, so I will try to find an alternative to a custom exhaust.

Intake - SMH> Im sure there aren't any billet/polished stuff out for the intake, is it? I'l like tp put a mesh steel cone UFO/flat intake on it. I have an adapter for the Animal Briggs but the holes don't match, Maybe I'll :grind: it to fit.

Thanks!!! for all of your help.

 

[g_rashid]

... That's a cool little chopper, you do need a longer exhaust but do not go too long or you lose some power. I put tailpipes on mufflers for the looks and to carry the soot away from the paint. If it were my chopper I'd make a springer seat for it to get me off the ground and for comfort while riding.

Yeah, I'm thinking of doing that. Bobber style!