Recent Posts

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General / Re: Carb cleaning
« Last post by Steve Holland on Mar 19, 2024, 11:37 am »
A lot of solvent expanded elastomers in carbs will return to their original size within 24hrs if left in the atmosphere, this was common in the small engine workshop I used to work in. We would leave the seals somewhere warm and ventilated, they would return to the original size overnight and fit back where they came from.
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General / Carb cleaning
« Last post by Ian Brooks on Mar 17, 2024, 11:10 pm »
This isn’t hovercraft but is relevant nonetheless. I’ve been fiddling around with an outboard engine for weeks, an almost unused tohatsu four stroke auxiliary motor. It would never run well, ok flat out but very poor idling. I bought it as ‘a bargain’!

I always suspected the carb, and had cleaned it a few times. It’s hard to find info on these small Keihins and so it’s difficult to fault find, some of it could be worked out but not with any certainty. Lots of chatter online about the idling circuit getting gummed up with fuel residue.  There was a hole that couldn’t be blown through even with the airline.

Anyway, I was on the point of buying a new carb when I decided to strip the whole thing to remove all the plastic and rubber before dunking it in acetone overnight. That did the trick! It shifted the lacquer and the idle circuit now blows free. Just like that!

The only reason to mention it - we do get similar things with Briggs carbs sometimes. Acetone might be worth a try next time. But you do need to get it properly apart otherwise all the seals and gaskets will be junk!
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General / The Worlds First Hovercraft Race.
« Last post by Eric Yeoman on Mar 14, 2024, 2:38 am »
The worlds first official hovercraft race was held on this day on Lake Burley Griffin in Canberra, Australian Capital Territory. Engineering students & backyard boshers descended on the capital with there magnificent machines & mostly, spent the day failing or spinning in circles. At least one of  todays makers attended. A 50 year anniversary event was planned but was refused by officials, no lack of those in Canberra, due to insurance worries. cheers.
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General / Re: htd drive calculator
« Last post by Philip on Mar 11, 2024, 3:21 pm »
Agreed with all points. I seem to recall that a 75x50x3 was needed to keep the deflection within tolerance. And then some accuracy in fabrication too!

Like you say, there’s no wonder people have trouble with these things. Too few Engineers.
Yes going up in size is what cures deflection, thickness of the box not so much. Cant find the figures here, filed somewhere :)
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General / Re: htd drive calculator
« Last post by Steve Holland on Mar 06, 2024, 12:33 pm »
The pto bearing type should be the third number after the displacement. If it's 0 or 7 that would indicate a plain pto, hopefully it's neither of those numbers and has a ball bearing in there.
Photo attached.
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General / Re: htd drive calculator
« Last post by Ian Brooks on Mar 05, 2024, 9:14 pm »
Nice. Simple cheap and will keep the deflection under control. Good to see a bit of Engineering going on!
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General / Re: htd drive calculator
« Last post by Ian Brooks on Mar 05, 2024, 9:13 pm »
Looks like your not adding any additional support to the briggs drive shaft?  The lower shaft position looks to be a simple hole.
I don't have anything to go on other than my gut feeling, but, surely the crankshaft bearings are not designed for that type of loading. And, if they are, then wouldn't the normal running stresses of the motor account for much of the design loading. The extra loading leading to a short bearing life?

The Briggs PTO bearing is enormous - it’s designed to take belt loads in addition to the engine loads.
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General / Re: htd drive calculator
« Last post by Al on Mar 05, 2024, 8:21 am »
Jon,


Private message me with your email, as I have the 37efi manual on pdf.  I can't remember where I downloaded it from, but hopefully the file will be small enough to email  (4.86 mb)
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General / Re: htd drive calculator
« Last post by Gaz on Mar 05, 2024, 7:11 am »
OK, I was just a little concerned it may be a lot for the bearings, if your happy, its your craft after all lol.

EFI: Not done anything with a reader or tinytac as yet. I'll get the colour codes for you. I also have a full complement of manuals for it too (with fault finder/ codes etc). everything is at the build site so give me a few days and i'll dig them out.
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General / Re: htd drive calculator
« Last post by joncurtis on Mar 04, 2024, 9:25 pm »
hi gaz
yeh did think of the suitability of the briggs bearing. im not making the shaft any longer, im just sticking the pulley directly to the shaft. Id be surprised if the briggs bottom end is not capable of taking the load from a pulley and a belt. but yeh it might not be ok. only time will tell. im more concerned the fan frame with rip the back plate off the engine ;)

people do drive belts directly off the briggs i have seen this done a few times. mainly in flying fish which are about as reliable as a beko washing machine. but never seen the bottom ends fail. im not over reving it :)

did you say you have an EFI, do you have one of the tinytac RMP/Fault code readers? do you have a wiring diagram for the engine.
when it gets a bit warmer and heath permitting im building a shed and will get the engine out and have a play with it
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