83 XC500 dyno results

I thought it was normal to fit a road tyre for a dyno run?

That was a realy messy dyno chart. the curves should go in a steady line. As you can see it missfires real bad actually. Check all the tips in this thread. but i would guess ignition issue.

hi fran k

fareham is in the south of england....the uk husky importer in my era was only an hour away.... well not exactly miles ... but you know what i mean... on typical european sandy tracks with washboard bumpy straights... any husky would eat up the rest with its long wheelbase and superior suspension.

My jetting woes:

XC500, just rebuilt with Woessner, rod and hone.
Altitude = 2000m
Pilot = 45
Main = 410
Slide = 2.5

The initial impressions after start-up have settled into the following:

bottom end is good
lower-midrange is good
upper-midrange is flat, burbles
top-end burbles, starts to clear nicely, clears, but then falls on its face and goes petang, petang, petang till the fuel catches up.

In a drag race with a Maico - I need to use the midrange, and shift early, if I try to rev out it takes so long to clear that its all over.

Opinions, guesses and suggestions welcome:

I'm no expert, (in fact I'm kind of ducking a bit as I write this becasue I'm overdue a follow up on this thread!) but revving-out should (to my simple mind) be all about

• fuel into the carb
• fuel and air into the cylinder
• exhaust out.

For fuel in - I'd check:

• Tank cap vent not blocked?
• Fuel filter not blocked?
• Carb float height correct and fuel jet (or whatever it's called) working nicely

For air in - I'd check:

• Clean air filter
• No air box lid? (They're for the 125 and 250s only)
• No blocked jets (and it'd have to be the main jet at top revs)

For exhaust out - I'd check

• Spark arrestor not caked
• Silencer packing fresh?
• No big dings in header pipe?

That's about as far as my comprehension goes. Internal engine seals baffle me but can apparently affect an engine's running.

Sorry if you've already tried the above, and I'm sure I've missed something obvious. People always seem to say to swap the spark plug first as it's easy and can cause sporadic running for no obvious reason!

Cheers
Lucien

@ Subaru, Ive never built 500 engines with anything but Mahle pistons.
But from experience youre over jetted. 410 is fine for coastal on a cold day, 370/380 should do the job on Aircooled. Pilot=35. Needle tube AA5, needle 7DH3 with clip on 2nd from top groove.

Maicos are quicker off the mark, but the Huskies ability to rev reels the Maicos in at end of 3rd gear.

Oh yes, the simplest of lessons: On carb float bowl make sure the floats move freely all the way without catching against the gaskets. This has happened and youll never get it to sustain rpm. Make sure floatlevels are right and that needle seat is new.

@Humm, that's what I thought too ????

Am I confusing over-fueling with running out of fuel ??

On a 2-stroke you would definately know the difference between over-fueling and running out of fuel..... (in-sufficiant fuel supply)

Run out of fuel (and oil) and things get hot quick.
Things melt quick.
Things go BONK ! real quick.

Bob Bean

1986 ISDE Italy
1987 ISDE Poland
1989 ISDE Germany

@Hedhunter9
I would agree normally,
but it takes a while to clear through the top of the midrange. On top it hits a wall and almost dies.
The float levels are almost to high, as on a slight slope the fuel comes out of the overflows..

Need to go find some jets and a long stretch of quiet road.
Compared to other bikes, indications are that the main is too big at 410.

My update:

Altitude 2000m
Pilot 50 (was 45)
Main 390 (was 410)
Needle 7DH3
Emulsion AA5

Findings:
Starts easier.
Runs a LOT better, but main still too big. On hard acceleration it will kill the spark ans start missing every now and again - so we are very close.

Aside:
The clutch setup is light enough to be considered for trails now. Teflon cable, extended arm and Barnet clutch pack with springs.

Making some very good progress now.

Any progress from you guys ?

T

Final setup as follows:

Altitude = 2000m
Pilot = 45
Main = 380
Slide = 2.5
YEAH BABY !
Race day in 4 days time.

Easy starter - no blubbering on test ride.

The followig was perfect:
Altitude = 2000m
Pilot = 45
Main = 380
Slide = 2.5
Some changes instore:
bars to combat arm-pump.

Clutch with Barnett kit, long arm and teflon cable is perfect !
Works style pegs - perfect.
Gold Valves with 10w, 4 turns of yellow spring - perfect
Shortened Husqvarna-parts Ohlins piggybacks - perfect

All I could ask for was a longer track to stretch the Swedish honey's legs.

My race partner:

Well it's been a while. Old Yella is finally running again. Turns out it was a loose wire behind the flywheel on the MZ-B ignition. It was shorting out with vibration at higher revs causing the sporadic running and haywire dyno chart from hell. Bike is now running smoothly so will be back on the dyno over the weekend hopefully. Will keep you posted.

Cheers
Lucien.

@WhiteHusky:

Tell us soonest please.
Post details of ease of starting, procedure to start etc
Also final jetting and altitude

T

Here's a short Youtube clip of the old girl running. Hoping to get it fine-tuned this week.

The seat isn't bolted down yet, hence the rear mudguard floating around in tune with that exhaust note 'music'.

The bike has the Mikuni 38mm carb on it and that's a DEP enduro rear 'silencer'.



Cheers
Lucien

Now things are getting confusing...

still been gettinbg that bong, bebong bong on the overrun, so dropped in a 460 main.
The blonde honey started screaming like I don't know what. Took a long time to get through the mid-range, but once clear started revving out like I have never had before.

Next step:
Drop to a 450
Clip on 2nd position
Hang on tight