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Discussion Starter · #1 ·
Hi all, can anyone tell me if there is a replacement carb that can be installed on a older 5 hp Briggs vs the carb that is attached to the fuel tank? I'd like to put a 5 hp Briggs in a Mini bike but it has to have a remote fuel tank.
Thanks GB in MN
 

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You might search some of the Walbro references. I think I saw one of their models that was of a similar configuration. Old mower salvage yards might be worth a look too.
 

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If your not concerned with having a govenor,just about any float style carb can be adapted..I made a custom "intake" for a 3.5 Briggs that had the Pulsa-Jet carb mounted on the tank,so I could bolt on a Walbro from a later Briggs push mower that had a bowl style carb with a float..had to use a peice of 1/2" water pipe and make two flanges that matched to carb and engine block mounting surface,and brazed them on at the right angles so the carb sat level...

..it ran very well,but I think the Pulsa-Jet was a bit better when it came to climbing hills or riding off-camber,as its diaphram fuel pump helped prevent flooding or bogging..Tecumseh used to have a diaphram style carb that would bolt right on in place of a float style one,I eventually found one of those and it worked great..
..Remember though,to use a carb off a similar sized engine so the jetting will be close,and dont forget when there is no govenor,its easy to send a rod thru the block!..
 

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Discussion Starter · #6 ·
Hi Guys, thanks much I'll check the model numbers and see what I have, this mini bike has a 5 hp Tecumseh that is the engine from **** I just can not make it run and there is not enough room for a Briggs with the gas tank attached to the carb.
GB in MN

 

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Thats a nice Heald!...you just dont see many Trail Bronc's like that in that kind of shape too often..

The carb on that engine is like the one I adapted to the Briggs engine I mentioned..
I would try to get one like that and keep it original ,myself..though I know all too well how frustrating those Tecumsehs's can be!..

That engine is one of a few I have seen that has the carb & muffler on the "wrong" side!--most Tecumsehs they had the muffler on the left port and carb on the right side..why they did that I dont know..(maybe the larger valve normally used as the exhauist one allows more air/fuel mix to enter the cylinder,and the smaller one used as the exhaust resticts the breating enough to keep it from tossing a rod too fast?..
I have a HM80 Tecumseh thats set up like that..

If the problem with your carb is it snuffs out when you try accelerating,but will idle fine,could be caused by a coil or condensor thats weak ,or plug wire thats cracked and letting the spark jump to ground,and/or the spark blows out under the increased demand on it..one of my H60 Tecumsehs did that with 3 "known good: carbs,so I started looking for other faults to blame..narrowing the spark plug gap to .010 "cured" the bogging,but it doesn't run smoothly with the plug gapped that close--still,its better than the engine dying every time you throttle it up!..I'm going to replace the coil when I find another one..
 

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Discussion Starter · #8 ·
Hi Tractor-holic, I would like to keep it as original as possible, I have tried everything to get that Tecumseh to run and its doing exactly as you described finally got it to idle but as soon as you try to increase the rpm's it will die, I've changed the coil, new points and condenser, had the carb off so many times cleaned and adjusted including new power jet still will not run or start well have just about pulled my shoulder out of its socket. I've tried a spark tester inline with the spark plug and it shows spark up to the point it dies, I installed an electronic module and it would rev up just great but starting it was a bear would kickback and rip your fingers off. So thats why I'm thinking of alternative engines, problem is this bike frame was pretty much designed around the Tecumseh engine.
 

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Have you tried raising the float level? With these simple mixers it can have a noticeable effect. Biasing the low-speed mixture fatter will help the flat-spot in acceleration too. Another member posted about the the inition's KV falling off exponentially with the mag's gap to the flywheel. Tightening that gap a mite might prove beneficial as well. I wonder how well the magnets retain their 'field strength' with age?
 

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Discussion Starter · #10 ·
Hi H-D, I've adjusted the float level as high as possible any higher and it floods, I'll check the flywheel mag gap have not done that, the magnets are strong, I'm thinking of opening the point gap a bit have them set at about 0.018" now may try a loose 0.020" another thing I'm going to try is a new spark plug. Thanks guys for the suggestions.
GB in MN
 

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Have you adjusted the static timing??..the magneto is adjustible where it bolts to the crankcase,the bolt holes are slotted,you set the piston to a specified distance before TDC,and then set the mag so the points JUST open at that spot..a self powered continuity test lamp can be used..

But--seeing you say the "point eliminator" chip helped rid you of the bogging problem,I'd say that means your ignition is more the problem than the carb is...might want to see if the tiny holes in the carb venturi next to the throttle butterfly are open and clear--there is a welch plug on the exterior that can be removed to see if any crud is plugging that passage up..(I avoid removing welch plugs as I seem to have poor luck getting a new one to stay in or seal properly,I clean the holes from the venturi side ising a wire from a wire brush)..

Valve clearances can afftect starting too,it could be the compression release may not be working ,or innefective if too much lash exists,maybe thats why it kicks back with the point eliminator module..(?)-I have had other engine kick when I tried using those modules also,I think the magnets in the flywheel weren't compatable--sometimes swapping the wires on the module (reversing the polaity) helps that..

Another thing is,some Tecumseh carbs need a fiber washer on BOTH sides of the fuel bowl nut,not just on the outside!..leaving the inner one out afftects the position of the main jet nozzle..I assume you have a "service" nozzle that has the "ring" around the holes in the jet--the original wont,and once removed,chances are good the holes in the jet and carb body will never align properly,and it'll drive you insane trying to get it to run right..
 

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+1 with Tractor-Holic on the discharge nozzle. I stumbled over that cautionary note earlier this week on an older engine restoration board. Tecumseh issued a service advisory to replace the nozzle with a hole with one having a groove all the way around it to prevent a mis-register (with the parts situation, some are cutting their own groove on a lathe). Months ago there was a thread regarding the e-gas attacking the 'O'ring that seals the nozzle to the carb body, causing severe running problems. Perhaps pull the plug & seal the replacement with a sparing application of JB Weld? Was the old hardening formula of Permatex sealer gas proof? I can't recall.
 

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I'd avoid using any gasket sealer on a carb,for fear of it plugging up any passages it might seep into permanently..Permatex #1 that hardens will resist gas,so will the Indian Head gasket shellac,but again,I'd not use it on a carb..maybe I'd put some J-B weld over a leaky welch plug,on the outside,thats about it though..
 

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Hi H-D, I've adjusted the float level as high as possible any higher and it floods, I'll check the flywheel mag gap have not done that, the magnets are strong, I'm thinking of opening the point gap a bit have them set at about 0.018" now may try a loose 0.020" another thing I'm going to try is a new spark plug. Thanks guys for the suggestions.
GB in MN
Did you change the points spring as well? I had a Briggs that would not run WOT, it had the wrong spring on the points and it wasn't strong enough.
 

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Discussion Starter · #16 ·
Hi guys haven't been ignoring you, I had Grandpa duties so was busy:thThumbsU
Ok to go over a few suggestion: the points are new and the spring is good so pretty sure we can rule that out also installed a spark tester and it makes good spark.
Thank you Motown, for the minibike link I jointed very interesting site.
I'm thinking its the carb yet did some reading on the minibike site about these Tecumseh carbs and have a some things to check, also will be checking the suggestion from you guys, I appreciate the ideas and will be checking them out, as I would like to keep the bike original vs going to another type of engine.
Will be checking out the discharge nozzle to see how it lines up I did buy a new one but did not look to see if it just has holes or the ring(I didn't know).
The tiny holes are open as is the lower idle hole but I learned that the metering rod in the idle tube can become stuck so will be checking that out. Maybe I'll just have to pop for a new carb but just hate to spend $70.00+ for a carb.
In looking on the minibike sight I see a number of Trail Broncs with the 5 hp Tecumseh snow blower engine installed so that is also an option.
Thanks guys I'll update as things progress(at least I hope it progresses)
GB in MN
 

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Discussion Starter · #17 · (Edited)
Ok guys, after reading somewhere that if you shake the carb you should here the idle metering rod rattle/ make noise, so I removed the engine then the carb and dissembled the carb shook it and not a sound (tried another carb I have and could hear the rod moving) so thinking that the rod just maybe stuck I tapped on the housing with a screwdriver handle and low and behold the small ball that seals the tube fell out onto the work bench looked in and no metering rod to be found so I cut apart an old junk carb and got the metering rod installed it in the carb reassembled it put it on the engine thinking I finally have it going. It started up on the 2nd or 3rd pull and idles like a jewel but will not go beyond fast idle just dies no matter how I adjust the jets. When its warmed up it will start on the first pull and idle nice but that's it Any ideas now?
By the way the power jet has the groove all the way around, in reading the manual in order to adjust the timing you need a special adapter on a dial indicator which I don't have otherwise I'd do that, it could be ignition now, I have a new condenser and new points set at a close 0.018" have cahanged the coil with another one.
GB in MN
 

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Try closing up the gap on the spark plug,if it accelerates better that way its weak spark--note that it wont run smoothly with a narrowed plug gap,and you'll probably have to tweak both mixture screws and idle speed some just to get it to stay running..

The H60 I have that would not rev up until I closed the plug gap has a bright snappy blue spark--but its more like a lightning bolt thin spark,that has no "heat" to it,evidently it can ignite fuel under low compression OK,but when you go to rev it up the spark gets snuffed out under the increased compression..make sure there is no vacuum leaks at the intake gaskets too..
 

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Discussion Starter · #20 ·
Thanks Motown, have been buying parts from them for years great guys to deal with they'll go out of their way to help you.
GB in MN
 
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