Carb Spitback Help??? its getting to me now.

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Monty
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Yes I used a Zenon one from a mate early doors and it was the same as mine. Mine is an in line 2 wire none powered type. it gives a red flash while his had a battery pickup. was brighter but drifted the same. Now got 2 scoots in bits and off to Spain Tomorrow for work so thats another week gone. the kin summer will be over soon.
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Monty
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For all those who have commented on problems with pickup heights on various setups and lightened flywheels. Does anyone have any measurements on how high the pick up needs to be.
The pickup has 2 slugs of metal embedded in its front. All 3 stators seem to be the same height mounted on the back plate
What I have noticed from the 2 flywheels I have tried is that the cast fins on one flywheel (the one that gives the least wander) is 3 or 4 mm further out than the other. I can nearly see the part of the flywheel holding the magnates between the flywheel and mag housing. I removed and refitted it without the key and it was the same, the 2nd flywheels look the same depth, so are they going on the taper far enough?
Im now thinking it has to be the magnates making the switch fire point is not lined up with the pickup.
I will try and measure back from the flywheel fitted through the holes and get an idea where the magnates should be.
dapper
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I helped a mate build his engine over in French France and when I went to put the flywheel on it wouldn't go at all. When I checked the two pick up triggers on the pick up were well high and had to carefully file them down and keep refitting the flywheel until it was all OK. Made sure no filings got anywhere, and when started it was fine. No issues at all afterwards. Never seen it on a pick up since. I must have had to file off about a sixteenth of an inch to get it right. Strange one. :shock: :o
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mick1
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I've been having problems with my Avanti, lots of spit back and boggy at low revs (struggling to get a tickover). The timing was set at 17 static. Spoke to Dan who advised not to re-jet any lower than i was. I've now fitted an M-Tech (set at 24 degrees) and it's got me a tickover without adjusting the carb. The bottom end is a lot cleaner (still not ideal). Still got some spit back but looks better than it was.

With you saying your timing was up and down this would account for the spit back and other issues. i'd look at fitting an auto retard but first identify the moving timing (loose magnet in flywheel ?).
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Monty
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mick1 wrote:I've been having problems with my Avanti, lots of spit back and boggy at low revs (struggling to get a tickover). The timing was set at 17 static. Spoke to Dan who advised not to re-jet any lower than i was. I've now fitted an M-Tech (set at 24 degrees) and it's got me a tickover without adjusting the carb. The bottom end is a lot cleaner (still not ideal). Still got some spit back but looks better than it was.

With you saying your timing was up and down this would account for the spit back and other issues. i'd look at fitting an auto retard but first identify the moving timing (loose magnet in flywheel ?).
That was where this sorry tale started. I hold a Piston. took advice about advance and retard being the way to go so bought an M Tech. Great low down but was having problems at top end and after 3 months took it off to notice my timing was advancing and retarding at will without the box of tricks fitted. So basically the black box was fighting with the wandering timing.
I have been measuring pick up heights of my 3 stators and they are all over the place. The mounting height varies by 3mm. Measured from the back plate to the centre of the 2 pickups. The 2 flywheels also go on in different positions by nearly 4 mm. Im sure now that my magnate pick up point is missing one side of the pickup points. It looks like I have to get the flywheel further on to the taper ? or lift the pickup by 2mm or so. As the BGM one is new I will adjust that to fit the flywheel and get the pickup opposite the 2 finger s of the magnates and see how it goes. Away with work all next week so it will be doing my head in all week. :evil:
johnny650
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Monty ...how did this saga end ? I read it through with mounting anticipation that you'd find the solution to the spitback which my SR 185 with 22mm Jetex is suffering too.

Like you I have changed engines twice from a 200cc kit to a 185 kit .Removed and replaced the 185cc five times now. Changed piston , changed carb 4x times (I have 5x Jetex) and changed stator , points condenser flywheel spark plugs Endless jet , slide and atomiser combinations and have pretty much the same issues that you had.

Cured a leaky drive side oil seal and base gasket and the last leakdown test shows I'm airtight now but still the starting and running issues and spitback over rich mixture
HotPearlSnatch
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I really feel for you guys with all this time, trouble and money.

I have no experience of the muggello kit but a fair bit of jetex carbs and in my experience those carbs are really quite unstable. The slightest deviance in the carb body jet profiles [like a badly chased casting from new, or some grit lodged in the carb body jets from use] can make huge differences to the performance of the engine.

Have you treid anything other than a jetex on there and if so what was it?

I had a lot of issues with dellorto open mouths on my AF stage 4, in the end i went back to my fav from the 80s the AMAL mk2, problem vanished and that was to do with heat disserpating from the [thin cast] delly as opposed to the much thicker cast of the Amal.....might be worth considering.
holty
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i would consider adding an external pick up from anthony tambs, it will rule out a timing issue, you can use it permanently and leave the red wire from your stator as a stand by, ive got one on mine and its a very steady 17 degrees, with odd combinations of flywheel, stator and magflange, pick up alignment can be a pain, thats why bgm stators come with packers.
johnny650
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holty wrote: Wed Aug 22, 2018 5:47 pm i would consider adding an external pick up from anthony tambs, it will rule out a timing issue, you can use it permanently and leave the red wire from your stator as a stand by, ive got one on mine and its a very steady 17 degrees, with odd combinations of flywheel, stator and magflange, pick up alignment can be a pain, thats why bgm stators come with packers.
good idea holty I'll defo use one when I finally get around to fitting my 12v electronic kit but at the moment I'm using a standard 6v points condenser system because I didn't want to introduce yet another unknown untested bit of kit into the mix until I got this running properly on original equipment that has been proven to work previously

I am completely exasperated with the Jetex carb now. i used to really plug and support them once.
They are a complete nightmare when things don't go right.
Difficult to remove ........ a nightmare to fix the throttle cable nipple when fitted .......zero clearance of the banjo to the engine mount.......impossible clearance of the petrol tap shaft and throttle pivot......etc

I'm going to sell all 5x Jetex carbs and all my jets etc and buy a PWK instead see if that is more stable
johnny650
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HotPearlSnatch wrote: Wed Aug 22, 2018 11:57 am I really feel for you guys with all this time, trouble and money.

I have no experience of the muggello kit but a fair bit of jetex carbs and in my experience those carbs are really quite unstable. The slightest deviance in the carb body jet profiles [like a badly chased casting from new, or some grit lodged in the carb body jets from use] can make huge differences to the performance of the engine.

Have you treid anything other than a jetex on there and if so what was it?

I had a lot of issues with dellorto open mouths on my AF stage 4, in the end i went back to my fav from the 80s the AMAL mk2, problem vanished and that was to do with heat disserpating from the [thin cast] delly as opposed to the much thicker cast of the Amal.....might be worth considering.
this isn't a muggy its just a simple SR 185cc cylinder kit with piston porting.

I have been using Jetex carbs for several years now without any major issues . Once they are blueprinted and set up properly they work well and are a good carb, The problem I have at the moment probably isn't confined to just the carb to be fair.

I have had a drive side oil seal leak which required a complete strip down . I'd inadvertently left the Haltite gasket out ! :oops:
Then I had a leak at the base gasket due to cylinder being over-ported by previous owner . A alloy gasket took care of that.
Then i had some issues with the ignition system which are also now resolved.
it was a combination of problems but its running now at last .
thanks for your input its appreciated
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