Rotax 185 CDI Conversion...easy!

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Postby xgary » Thu Feb 10, 2005 1:07 pm

ray, nice cdi convert

one thing is what is actaul rpm at idle ? does not matter as long as it runs solidly. u prolly gettin more than 1100 rpm ...
make sure your idle mix screw is rich enough that you have no bog from idle to high speed circuit.

you wanna make sure when you cruising and pull the throoles to idle they stay ther and not burp fart etc and quit.

keep it coming
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Postby lazair3ca » Thu Mar 31, 2005 8:47 am

We have both of George's engines running now with CDI. The idle RPMs are indead low and smoother than with the regular ingnition. When we get reliable numbers and we have the timing adjusted I'll post them.

We had trouble with the decompression valves. I have an idea now why they are replaced with a plug. Wildfire can not supply the old decompression vavles. We have to move one valve amongst two or three engines to continue the testing.
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Postby Guest » Fri Apr 01, 2005 1:35 pm

Guys,

Here is the location you can get original Decompression valves from. Ask for part number 11236

Dapco Industries
ask for Scott
734-426-8900

There is a catch at the monent. Scott has none of these made up. He does have enough component to build about 400 of these units however. Now, he does not want to sell a few of these to a bunch of differnet buyers, he will sell one batch to one guy and that guy will have to act as a distributor for the rest of us on these valves.

If anyone is interested, you can call him and negociate the deal.

Good luck...
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Postby bdiedenhofen » Fri Apr 01, 2005 2:31 pm

I called Dapco a while back and got the same story. It's a whole lot of cash for one person to fork out in the hopes that some others may be interested. Personally, I've had to tear my engines down three times due to decompression valve falure. I checked them prior to each flight and even though the punched portion looked ok, they still failed in flight.

I tried to put a drop of weld on the top as many have suggested, and two valves failed this way too. It's impossible to inspect the weld, you just have to hope it's on right.

For the past twenty hours, my engines have been running with the valve holes plugged. No sign of any stress, damage, wear anywhere. I squirt a little gas into the intake from a spray bottle, turn it over by hand a couple of times and it fires up on the first pull every time.

Some guys have stated that they had signs of stress fatigue showing up on engine mounts, starters etc., without the valves. So far, I've had none of this. I think I would prefer to replace a mount down the road rather than deal with another in flight failure and possible ring/piston damage again.

I'm told that other small engine manufacturers used the same valve and some guys have found it at the local small engine supplier. So far, I've had no such luck, but for those looking, small engine and motorcycle shops apparently sometimes do have them.

On the topic of the electronic ignition, I am looking forward to hearing how they work out over the long term. I've had no trouble with my points so far, but the electronic set up has been way better on any other engine that I've retrofitted.

Brian D.
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Postby xgary » Fri Apr 01, 2005 3:14 pm

I fixed de-compresion valves buy welding them SHUT
take out valve and braze or weld the hole shut.

No need to decompression vlaves unless you need to do re starts in air.
A firm pull wil work fine on 185s or even JPXs ... 2 hands best tho and a FIRM Grip.

I had the valves fall apart too and i thinkg they justa waste of time.

If one was worried about their weak grip or arm, possibly machine up a larger pulley but you won't gain much as there is not alot of room.
Just live with it and maybe use gloves to save ur hand when the cord gets ripped outta ur hand.
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Postby Guest » Fri Apr 01, 2005 3:31 pm

These guys may have the Dapco valves for $16 each. I'd mail them and ask for more pics or just buy one to see if it was the same as original. The Dapco valves were used on Powerbee, Tecumseh, Pioneer, Rokon, and other small motors. They are out there somewhere. You will need to search, call, and ask questions to find some. Search and look guys, use this powerful tool in front of you to your advantage.

http://www.vkemotorsports.com/
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Postby Guest » Fri Apr 01, 2005 4:57 pm

bdiedenhofen @ Apr 1 2005, 02:31 PM wrote: I called Dapco a while back and got the same story. It's a whole lot of cash for one person to fork out in the hopes that some others may be interested. Personally, I've had to tear my engines down three times due to decompression valve falure. I checked them prior to each flight and even though the punched portion looked ok, they still failed in flight.

I tried to put a drop of weld on the top as many have suggested, and two valves failed this way too. It's impossible to inspect the weld, you just have to hope it's on right.

For the past twenty hours, my engines have been running with the valve holes plugged. No sign of any stress, damage, wear anywhere. I squirt a little gas into the intake from a spray bottle, turn it over by hand a couple of times and it fires up on the first pull every time.

Some guys have stated that they had signs of stress fatigue showing up on engine mounts, starters etc., without the valves. So far, I've had none of this. I think I would prefer to replace a mount down the road rather than deal with another in flight failure and possible ring/piston damage again.

I'm told that other small engine manufacturers used the same valve and some guys have found it at the local small engine supplier. So far, I've had no such luck, but for those looking, small engine and motorcycle shops apparently sometimes do have them.

On the topic of the electronic ignition, I am looking forward to hearing how they work out over the long term. I've had no trouble with my points so far, but the electronic set up has been way better on any other engine that I've retrofitted.

Brian D.


Did you know the valves are stainless. Were they tack welded with stainless rods ??
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Postby Guest » Thu Apr 28, 2005 9:41 am

Actually the Valves appear to be Nickle plated.
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Postby rayjb60 » Mon May 16, 2005 4:48 pm

Update to the CDI conversion project:

They run beautifully and idle very steady.

Throttle response is immediate and instant from idle to full throttle and anything in between, without any blubbering or hesitation what so ever!

On the slower of the two engines I get 5680 rpm on the ground and 5840 rpm in the air at 3000 ASL.

The climb rate on my vario says 420 ft/min at 35mph....I figure I can get better at 25mph and steeper climb....I'll try it next time.

The faster one is 90 rpm more.

Here is a picture of the plug....not to clear....but you can plainly see that the plug has a nice light brown color and little deposits on it.

This is after 6 hours Total time, with 35:1 ratio petroleum based(non-synthetic) 2 cycle air cooled premix oil.... I get it from a motocross bike shop for 5.99 USD a quart/liter.

I plan to put K&N RU-2580 airfilters on the next time I fly, to save the great performance from the dust out my way in the high desert of California, El Mirage.
K&N Filter RU-2580
It was sized at least 5 times bigger than required to minimize the airflow restriction, plus I happen to have a 2" flange so it was a logical choice. It actually has enough surface area to provide enough air for a 70 HP engine.

I do not have the velocity stacks, mine came with a 52mm flange.

I'll report the RPM/performance changes if any for this mod.
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Postby Guest » Tue May 17, 2005 10:54 pm

What Idle RPMs are you showing with the CDI's ?? Idling smoothly is something a Rotax 185 usually does not do.
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