I have a Brison 3.2 that ran perfect until yesterday. I had 4 great flights and on the 5th it began stumbling and not coming up to normal RPM. It still start perfectly and idles pretty normal but at mid to full throttle it just isn't what it was. Sound like a fouled plug? I never fouled a plug before so heres is a pic of it.

It is hard to tell by the photo, but I would definately start there. Plugs are cheap. How about carb settings, could it be lean? Another thing to look at is your fuel system. Is is possible that one of your fuel lines got a hole in it an the engine is going lean? Is the engine burbling at high throttle?

Yes, burbling at full throttle. I just called advance auto and they said they cross referenced the plug number to an "autolite" plug and they are only $1.50, so i'll go get a couple of them and give it a try.

Another thing is I jsut changed my gas brand 5 flights ago, from motul to penzoil. Maybe that had something to do with the plug fouling. My mixture was pretty close to perfect for the whole life of the engine.

Make sure you get a resistor plug. If you don't you will gets a lot interference. Also check your ignition battery voltage. If the battery gets low, it will cause running issues, usually a misfire.

make sure to replace with a R-type plug (resistor)

Looks like the plug may be oil fouled as best I can tell from the pic. The change in oil type may require that you re-tune the engine a little. Just about any auto parts store should have a Champion RCJ7Y in stock. Seems odd that they had to cross reference to find an Autolite instead.

Thanks guys, I will make sure of that. I don't thibnk the autolite is am R plug after searching it. I just had another idea though, this could be my ignitoon battery. It has been seeming weak lately.. I'm charging it up and I'll take it outside and see if that fixes it. It is an old battery and has been losing capacity.

One of my Brison 3.2 ignitions starts to run poorly if the battery gets down to 4.75.

Yes a battery will jack up the way it runs it will only let it run at low rpms

OK, after all this trouble I never actually checked where my needles were from closed. They both eased themselves out to almost 2 turns open. I know for a fact this engine wants them to START at 1 turn open and lean from there. I just now put them to 1 turn out each and it now runs jsut as perfect as it aways did. I am surprised they vibrated out.. never happened before.. oh well.

I agree with Silversurfers comments. I think that plug is on the verge of being fouled. It should not look black on the electrode or ground pin. It should be a tan color and dry. Your plug looks black and a little shiny--perhaps just a bit wet or oily.

The mix ratio shouldn't make your plug look like that. I run 40:1 and my plugs look tan and dry after many gallons of running. I've seen plugs puled from engines running as heavy as 24:1 and they look tan--not black as yours is.

You've been running rich on the top end. Put the new plug in and adjust it again.

Check your plug gap on the new one. Too much plug gap will make it hard for the plug to "jump" to ground and make a good spark. Too little gap will just give it a weak spark. When you get the gap in the sweet spot--it's a nice thick blue spark. I run my plugs around .028" ---.032" gap

Yeah, I went and got the new plugs and when I put it in and ran it just now, it still stumbled. At that point, I thought to check if the needles had possible come out on thier own and sure enough, they were out way to far, causing it to be stumbling rich. Put them to 1 turn out each and it ran great!

I just got smacked by a backfire trying to start this thing. I think it happened because I put the prop on by accident a bit to far down. I usually put it just a bit higher than 3:00 for compression, but this time, in haste, I put it on at 4:00. I had the choke on and was flipping to get a bark. It must have been a bit lean still and it backfired right against my fingers. As you can see in the pic, it broke the prop.. now I need a new one. My finger is all fat and bruised, but no serious damage seems to have resulted. Stupid mistake for me. Remember to get the prop on RIGHT where it needs to be!

OUCH...Doing that to a MSC prop is gonna leave your hand not feeling well at all....I hope your OK

Guys, I just talked to whaturi (him and I fly a lot together and I sold him that engine) What happened is the high speed needle backed out causing it to go rich. This is one of the Brison's Gary did and used the lightened pump spring on it so the needles only need to be no more than one turn open. His was out 1 3/4 turn but replacing the plug is not a bad idea anyway.

This Brison has been rock solid as most Brison's are

I suggested he strecth the spring and at the same time take is dremel to cut grooves on the part of the spring where it contacts the carb body and the needle so it will not back out again. I've done this with loose 3W needles and it works well as it acts like a lock washer and "grabs" the carb and needle

I sorry that happened but I'm sure glad it was you and not me. I run MSC props too and that's a lot of blade to pound into your hand! Maybe see the Doc to see if anything is broken. There's a lot of tiny bones in a hand.

It was the tip of my finger. It is already feeling better now, although I think it will be sore for at least a week. I learned my lesson on that one.

wow glad u were alright and able to update us. those springs sound pretty weak and should be replaced. how r u liking your prop i have a Vess 22a & 23A i will be trying sometime this month on my 3.2

Well, I had the MSC 22-8 on it so far, but now it is broken from my finger. The guy I bought the enging from gave me a vess 22 b to try out. I had a Vess 23 c on an MVVS 58 and loved it so I have high hopes for this 22 b.

whaturi,

I went out a little while ago and looked, the Vess on my other Brison is also the 22B and that's on the Ultimate. You have seen that one fly on a very draggy plane so with the C-Arf being much better aerodynamically, I beleive the 22B will be just fine

Wish I had a 22A just in case for you to try

keep me posted on your results i am doing the A series on my Vess props. I also have to try 27a that came with the other props last week. I will get to in hopefully this month on both all the props 22a, 23a, and the 27a.

krazy,

If I remember correctly, my Brison will turn the 22B at somewhere aorund 6700 to 6800 and it's just barely broken (something like 6 gallons) in where the engine whaturi has is closer to 8 or 9 gallons and he was just starting to rip the MSC22x8, I lost 400rpm between the PT model 22X8 and the Vess but the pull I got from the Vess far outweighed the rpm loss on the GP Ultimate that engine is in

I run the 23A on my 55i for right now on a tuned pipe and I'm getting 7100 on that one. Crazy vertical on a 19lb plane. I have a 27a on the way for my 3W 80xi CS version versus the 26x10 PT model on it now. I expect I'll see even better out of the Vess on that engine as well espeically on a WH 33% Edge

OUCH!! I got smacked by a 22-10 on a 54cc conversion engine once. I was "eyeballing" my timing ring to adjust my sensor and pickup. Dumb Dumb Dumb. It backfired and went backwards through my fingers just as yours did today Whaturi. That smarts a bunch and I feel your pain man. It's gonna be sore for a few days. I started using a glove and made a degree wheel for future projects. Too little too late. I was bent over with my hand between my knees. Dancing around in the driveway and saying a few choice words. I was positive my fingers were broken at the time, but after sitting on it a few days, I came to the comclusion that the only thing wounded was my pride. [sm=red_smile.gif]

I don't EVER want to get smacked again.

Rcpilet
u made that just like radio i felt i was there hearing the deal.

bubbagates
yeah i am doing a header tune pipe on the brison so i figured i better had both the 22 and 23 on my side in case the pipe makes me do the do.

I forgot you were doing the pipe on the Brison.

yeah baby going on the Extreme Yak