Backfire when starting

[Hughieboy]

Hi,

My scooter seems to have developed an issue whereby it backfires when starting. It always starts but for some reason when you kick it over the kickstart immediately 'gives' and fires/backfires on the first time usually before it starts. Its an Li150 with a 190 top end, 30 mil Dellorto and Varitronic with a TSR Evo pipe. I recently checked the timing as I was getting heat seizures which is set at 19 degrees and retards down from there. Seemd ok but I still get heat seizures when cruising at 3/4 throttle.

Bit worried in case I bugger it! Hope someone recoginises this?

[MickYork]

19 seems a tad low as the Varitronic retards by 7 or 8 degree (i think ?). This would then retard to 11 or 12 degree which is very low, 16/17 being a "popular" running mark. This doesn't explain the backfire or the heat seizures but it's worth looking into.

have you done plug chops to checked your air/fuel ratio ?

[Hughieboy]

19 is whats recommended by Cam Lam....
The plug looks ok, historically I've had an issue whereby 120 main jet runs smooth but I get heat seizes, 122 main bogs a bit but doesn't usually have the same heat seizing. Never had this backfiring though.
I wondered if there was a 'usual' cause of this issue....

[MickYork]

Could be an air leak, worth doing a leak test to eliminate that option

[Hughieboy]

Thanks Mick...

I already did that too! Has a small leak at the exhaust port/manifold now fixed....

[Fast n Furious]

There's not much meat left on a 190 cylinder. So, Your cooling needs to be spot on to prevent seizures.
Minimise the gaps where cooling air exits, which hasn't done any useful work.
It makes all the difference.

[Hughieboy]

There's not much meat left on a 190 cylinder. So, Your cooling needs to be spot on to prevent seizures.
Minimise the gaps where cooling air exits, which hasn't done any useful work.
It makes all the difference.

I hadn't thought of that.... I'll see what I can do, thanks.

[Scooterlam]

What's your start up regime?
Choke?
Twist of throttle as you kick?
fuel on or do you wait till it fires?

[Hughieboy]

Fuel on, choke (thumb choke), twist and kick.... Always done it the same...

[Scooterlam]

Probably takes a partially blocked pilot out of the equation.
ANTHONY Tambs has done lots of tests on various stator and reading his stuff stators can take up to 800 odd Rpm before they create a clean spark.
If it's something that's developed might be an issue with stator showing the first signs of being on the way out.
Personally for the small investment I would fit one of his external pick ups. But check they'd be compatible with your advance retard.

[Hughieboy]

Thanks..... but I hope there isnt anything wrong with it as it's a nearly new Varitronic, it's done less than 1000 miles. I'll look it up....

[Mori63]

Hi, my varitronic started to do exactly the same a few years ago first kick it would misfire second kick it would start and I just lived with it ,then when in Normandy it started proper playing up ,it started as normal but then warmed up it was a right pain to start taking 30-40 kicks to get going it wanted to start but just wouldn't catch until you got lucky.the only advice I could find was try another stator plate ,I didn't have one or know anyone with a spare and new ones at over £200 i renewed the lot with BGM stuff .i know what I did won't really help you but I would say it sounds like the start of your stator braking down.

[Hughieboy]

Hi, my varitronic started to do exactly the same a few years ago first kick it would misfire second kick it would start and I just lived with it ,then when in Normandy it started proper playing up ,it started as normal but then warmed up it was a right pain to start taking 30-40 kicks to get going it wanted to start but just wouldn't catch until you got lucky.the only advice I could find was try another stator plate ,I didn't have one or know anyone with a spare and new ones at over £200 i renewed the lot with BGM stuff .i know what I did won't really help you but I would say it sounds like the start of your stator braking down.

Wow.... that's disappointing considering how expensive it was. Probably bought it three years ago but I hardly ever ride the thing so it hasn't seen much action. To be honest, I've never been over impressed with it considering it was about £400 all up from memory as it's been a bitch to get the timing right on. What did you buy?

[Scooterlam]

Speak to th3 supplier, ask them how to check it.
If it is faulty there may have been a bad batch like the bgm's that wrapped themselves around the crank.
If not might be good to look up the same of goods act.

Fit for purpose and for a reasonable time.
I would argue £400 for a thousand miles isn't reasonable.
Remember you contract is with the supplier not the manufacturer

All a bit previous but I'd get the multi meter out and ask what readings you should be seeing.

[Mori63]

I had mine over ten years and was never really impressed with the lights ,BGM flywheel ,stator and CDI is what's on it now .

[MickYork]

I bought a second hand one and did quite a few thousand miles on it....no problems. I only changed to a "common" stator as i was concerned about breaking down away from home and no-one having a spare Varitronic stator/cdi/flywheel/etc.