Starting a 490

[Mad Max]

Hello Gents
I've just picked up my new toy, a 81 490.
A few questions:
Fuel/oil ratio?
Spark plug type?
I'm having trouble getting a consistent spark, coil resistance is 33ohms, and the pick up is 6.5ohm, sound right?
Assuming the poor spark is normal, what is the starting secret, carb tickle? Throttle opening?
Any advice welcome.

Regards

[Branchy]

25:1 mineral  40:1 syn
b8 or 9 es
not good with tech stuff etc muck around with timing so it doesnt bite you
hold down tickler till you see fuel run out over flow then if that doesnt seem to get enough fuel (plug not wet) put your thumb over overflow pipe and do it again
live on a big hill
enjoy mate great bike

[Bruno1969]

I run 30:1 with a synthetic oil.

You can optimise the spark by making sure all the earthing points are clean or run a seperate fire up to the coil. My 490 has the Motoplat Enduro ignition which has the external rotor - theoretically at least giving a better spark and smoothing the slow running out a bit.

Trick is to flood the bastid. Fuel must come out the over flow pipe. From time to time I lay the bike down on on its side and have in the past held onto the front brake and got a mate to lift the back end up so its doing an endo - gets fuel into the crankcase.

Give two or three slow priming kicks, go past TDC and kick like it owes you money. Repeat until it starts or you collapse.

[Mick D]

live on a big hill

 

go past TDC and kick like it owes you money. Repeat until it starts or you collapse.

 

[sa63]

a worn out carby will give you no end of grief..... be sure its fresh.....

[Mick D]

a worn out carby will give you no end of grief..... be sure its fresh.....

Yes, that is a very good point.
No doubt I am far from being the only one that has seen a lot of bings worn out in the slide and slide bore.
They must have the rubber seal fitted at the top of the carby where the cable enters the carby cap cable adjuster, to prevent the fine dust from being sucked in. That fine dust/grit soon produces a gritty valve grinding paste like slurry.
It then doesn't take long to wear out the aluminum/alloy slide and bore.

[Mad Max]

OK, thanks all. That gives me plenty of things to look at.

Does anyone have a PDF owners or workshop manual for a 490?

Regards

[sleepy]

I'd go for 25:1 with a mid range Syn oil. The 490 big ends are a bit on the small side for such a large engine and will survive at 40:1 but will last a lot longer with the extra oil at 25:1. I don't want to upset anyone by listing oils that aren't any good but be carefull when taking advice from your bike shop sales man as they push the stuff that gives them the biggest profit.

No one has mentioned the de-compressor. Make sure you use it or you will brake the kicker. So to start do the tickel thing if it still has the Bing or if it has a Mikuni just flip on the choke. Pull in the decomp and get it just over compression then still holding in the decomp give it all you have. As soon as it fire let go of the decomp. If you can't get it to go come back on and let us know what type of ignition and carb the bike is fitted with. If you are a skinny little bloke you should go to your local Maccers and start filling up on burgers and chips because they do need quite a kick.

I have a manual but it's a hard copy, if you are near the Brisbane southside you could get it copied

[Davey Crocket]

Just do what most have been doing forever.....make sure you have plenty of mates in the pits to help push start the buggar....LOL

[HVA61]

If you use the decompressor , they as easy to start as 125.

If they are timed correctly and carburettor is set correctly it should go in a few kicks from cold and 1 or 2 when warmed up

No big effort required to start them.

Its debatable sometimes , that they will run effectively for extended periods

[JohnnyO]

I've fitted the bigger late model 16mm decompressor to mine and that helped. I also took a little compression out of it by fitting the std 1.2mm head gasket instead of the thin one I had in it.
I've got a motoplat internal rotor ignition set at the std 2.2mm btdc and a Bing carb.
Mine starts pretty well now, haven't had to push it for ages!

[sleepy]

If you use the decompressor , they as easy to start as 125.

The only 490's that Iv'e seen start like a 125 are in need of a re-bore.

The late model decomp valve is actually 18mm not 16mm and they do help a bit. I have seen one 490 with a 2.5mm piston in it and a PVL ignition that will not kick start because it isn't possible to kick it fast enough to make a spark even with the 18mm valve. Push starts no problem if you have a hill.

[JohnnyO]

If you use the decompressor , they as easy to start as 125.

The only 490's that Iv'e seen start like a 125 are in need of a re-bore.

The late model decomp valve is actually 18mm not 16mm and they do help a bit. I have seen one 490 with a 2.5mm piston in it and a PVL ignition that will not kick start because it isn't possible to kick it fast enough to make a spark even with the 18mm valve. Push starts no problem if you have a hill.

That's why I lowered the comp a bit, so the motor will spin faster when kicking.
Mine used to be a bitch to start and often had to push it..now it kick starts no problem.

[80-85 husky]

get a husky.....

[JohnnyO]

get a husky.....

I've got 3.. they're no better