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Paramotor service / tuning - Northwest


aquatix
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Is there anywhere around the Northwest that can accurately service & tune paramotor carburettors ?

Mine seems to be running fine, but in the last month 2 of the people I fly with have suffered holed pistons due to lean mixture. :shock: Can't afford that at the moment !!

I used to tune my old classic cars with a gas analyzer but don't have one anymore. Does anyone use this method ? I assume you would set it slightly rich at ground level so it leans out to normal at altitude, so is there a recommended CO percentage to aim for ?

Thanks

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I'm sure it's the other way round, i.e. the air gets thinner as you go higher hence the mixture gets richer the higher you go. Next time you fly, give it full throttle for a min and then kill the motor and glide back (or do it on the ground) then whip out the plug to check the mixture that way. I tune mine a fraction too rich on the ground so that it's less likely to hole pistons but occasionally does make it harder to start.

see here for plug colours

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:oops: Whoops - I meant thinner air at altitude !

I understand the plug colours and I used to use various gas testers, carb balancers and even a 'colourtune' glass spark plug to see the flame colour on my 4-stroke engines. Unfortunately non of these seem compatable with an oil mix and coming from a background of big V8 engines means a 200cc 2-stroke is never going to sound right to my ears !!

I can't seem to find any reasonably priced small CHT/EGT gauges anywhere, but not sure if these would be much use as I rarely use full power for more than a minute or so at a time, and the article you link to says the prop loading is the biggest factor in temperatures anyway.

Low speed mixture is OK to set on the ground, but it would be impossible for me to adjust high speed mixture in flight and its hard to feel the effect of small adjustments between flights. I guess its just a case of finding what gives maximum rpm on the ground with a crisp throttle response then maybe setting it a tiny bit richer to be on the safe side ?

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  • 2 weeks later...

For detailed info on carb tuning try these websites. You ll have to hunt around via the homepages for others but plenty of info including walbro manuals. For spare parts try rowena motors they re second to none and cheap too.

http://www.aerocorsair.com/id154.htm

http://webspace.webring.com/people/bf/f ... ation.html

http://www.wind-drifter.com/technical/wg8walbro.php

http://www.rowenacarbs.co.uk/

http://strato.co.nz/piccolo/engine_tuneup.html

that should keep you going. As I said plenty of stuff on the other wind drifter pages and aerocorsair. The bhpa mag skywings has recently ran 2 articles about fitting o2 sensors and mixture controls to a radne raket.

Hope this is of some use.

Glenn

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Thanks Glenn - I also found the following sites to be very useful for the carb rebuild I completed last week:

http://www.footflyer.com/fix/motor/carburetor/walbro.htm

http://www.pegasusautoracing.com/document.asp?DocID=TECH00038

Other than a bit of dirt in the internal mesh filter my carb seemed fine, and although I'm happy working on engines & carbs I found some of the advice conflicting. Most suggests scrapping the large rubber membrane in favour of the teflon one (both are supplied in the rebuild kit) although mine had the rubber one fitted which some sites suggest delivers more fuel. One suggested cutting out the flap from the C-shaped membrane (it was missing in mine before rebuild) but this was not mentioned anywhere else so I left it in. I also used my Dremmel to cut a small notch in the throttle butterfly to aid low speed idle - although being cautious I've not made it as big as it could probably be ....

This brings me back to the thread title - tuning - which is a bit of a struggle. There is no safe way to adjust the high & low screws whilst running, as they are too close to the spinning prop. Switching off between tiny adjustments makes it hard to see the effect of each change - especially when it effects different stages of throttle opening and RPM. Has anyone got any tips or tricks for this ?

I wanted to fit a CHT guage but the spark plug is recessed so won't take that type of sensor and I doubt the engine casting is suitable for drilling and tapping a thread. Similar problem with the exhaust for mounting an EGT sensor. Does anyone bother with these (my engine manual says they should be used) and if so, can you post any pics ?

Thanks again.

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If you're prepared to go to the hassle of drilling your exhaust to fit an EGT sensor you would be better off fitting a Supatuna analyser. It will sense oxygen levels in the exhaust gases and use coloured LED's to indicate whether you are rich or lean. It will tell you useful info at any point in the rev range.

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Not heard of a supatuna but I thought it was a problem to measure exhaust gases in a 2 stroke due to the oil mix ?

I was thinking more along the lines of the Stage6 / Koso gauges such as this one: http://www.scooter-attack.com/index2.php?main=/shop/artikel.php%3Fs%3D%26artnr%3DS6-4033%26modell%3D371%26l%3Dnavigation

They are cheap, self powered and can be fitted with different sensors for EGT, CHT under spark plug or in cyclinder block. Just not sure what would be best for my machine or if anyone has tried this ?

I know the XC Quest and Brauniger IQ Motor were designed to do all this - but at a hefty price ....

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I found gauges a load of hassle as readings are not black and white

http://www.challengers101.com/ExhaustGasTemp.html

I have used 'Colortune' with great care and laser pointer. The only sure fire way is, as Dan said "check plug colour. After all it lives in there"

http://tsrsoftware.com/images/read_plug ... ftware.jpg

A little tip. Use a piece of clear plastic tubing over your low screw to guide the screwdriver. Hard to do when the engine is jerking all over the place otherwise.

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For a very interesting youtube video of a complete Radne Raket 120 and Walbro WG8 stripdown go to

its speeded up but it show the process and I'm sure there are hosting sites you can tranfer the video to and then download it and slow it down on your own PC.

For those with Radne 120s who are looking for spareparts you might be interested to know that its based on the Husqvarna 3120/ 3120 XP chainsaw motor and i've been told by one of our powered hangie friends that the pistons/cylinders are interchangeable.

Cylinder+piston+rings and gudgeon pin on Ebay are £80 as opposed to £190ish from Radne. They are aftermarket parts but sold in the US/EU as replacements for the originals.

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Some useful tips and a good exchange of information - plus there is plenty more on the 'net. The rebuild was never an issue as I've worked on plenty of engines & carbs in the past, although only ever 4-stroke.

I've now spent most of the day chasing the tuning (and annoying the neighbours) but still can't seem to get it perfect at high, mid & low rpm. The problem is having to switch off each time, as even with a bit of tubing over the adjusting screws you cannot adjust it while running without becoming an instant amputee (its a design flaw where the carb should have been mounted to face the other way, but impossible due to throttle cable).

I can get the low speed running smooth, but then it just 'blats' when you open the throttle and slows down / stalls. Now set so it picks up OK with no obvious 4 cycling through the rev range, but a bit shaky on idle at 1500rpm. I set the high end to peak rpm which at one point went to almost 9000, even though the manual says this (200cc) engine has a top speed of 7500rpm. I turned it a tiny bit richer for safety and it now seems to max out at 7800rpm.

Fitted a new plug after getting it all to what seems OK, and gave it about 10 minutes at varying rpm, followed by a minute or so at maximum, killing the engine before throttling down. The shiny white porcelain is still white (or very light grey) with just the faintest tinge of light tan near the tip. How long should it take to produce a 'true' colour reading on the plug ? The old one was coffee coloured (strong, with milk) from normal use (not max power testing).

I guess the next test should be a longer run at 3/4 throttle to simulate cruising, which it will be doing most of the time - or am I being too paranoid about it all ?

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We have had strange cases in the past where a bad prop has had this exact same effect... (dan the man for one)

I would have sworn that the carb needed tweeking but the only thing that would fix it was a new prop.

SW :D

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  • 1 month later...

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