alloy 197 kit spitback/flooding

[shamrockexpress]

just finished rebuilding a series 3 LI 125 engine, std gp 107 crank, indian alloy steel lined 197 small block kit, asso piston and rings all new 3 thou clearence , squish 1.3mm, 22 mm sh 22 original dellorto. 45 pilot, 118 main , new slide gp150 also atomiser 5899-4 .
I have tried a new jetex 22, a spaco 22 and the current dellorto with different jets and choke plungers.........also swapped out the stators indian . still to no avail, the engine will start on the choke but when choke is off it will run only by keeping the revs up and then proceed to flood its self with lots of spaitback!!!! theres far too much fuel to let it idle...... my guess is the kit durations. 170 exh, 124 trans, and i,m not sure if i got this right as i wasnt comparing but inlet seemed to be 145
could this be the issue.
I know theses cheap kits are hit and miss is this a miss,,
any thoughts

[Adam_Winstone]

145 inlet should give zero spitback or staring issues.

Ignition issue, float, float needle?

[shamrockexpress]

changed to new float needle red tip longer version, original dellorto float no holes no wear, with float bowl off i can stop fuel flow coming in by lifting float so its sealing off. 110 and 500 readings on both stators ive tried, set bout 18-21 by eye as i cant strobe it to 17 until it runs long enough,,,,,,i may try another flywheel just in case........ at my wits end should have been a simple plug and play build

[Adam_Winstone]

Another flywheel will be a good test for it.

Fingers crossed for sorting it.

[Warkton Tornado No.1]

You can normally strobe an engine with plug out - but earthed to spark - with a power drill that has a 17 mm socket attached. Just don’t go mad as you’ll slacken off the LH threaded nut & - of course - don’t use an impact driver or a drill set on ‘hammer’. Although the revs will only be low, it should be enough to establish a ballpark setting. If the strobe is 12v powered, you can even place a battery on the leg-shields/floorboards & walk the bike in first gear to see if the spark is consistent & get a reasonable idea of the timing.

[shamrockexpress]

The TDC i have marked and also my 17 deg mark on the mag. when i line up the ,,,, " ,,,, two ticks at the inspection hole at (magnets firing point) the arrow on the indian flywheel is pointing more or less at my 17 deg mark so i reckon it should at least run and take over,,,,especially because it does start and run 20seconds or so until the flooding starts......i am now pointing the finger towards the indian kit or i hope i havent the piston wrong way round but i,m sure i double checked this,,,,,,the 145 deg inlet duration and fact that the manifold was so tight to the engine mount i had to slot the manifold to get the carb on.........cheap kits i reckon buy cheap you buy twice

[hullygully]

why are you using a gp150 slide bud?

[shamrockexpress]

initally i had gp200 7895-1 and due to all the spitback have tried leaning of with the 7895-2........was just more trial and error to stem the flooding.

[Adam_Winstone]

Sounds as though progress is being made

[shamrockexpress]

99% problem lies with the large inlet hacked into the cylinder by the indian suppliers of these kits, 145 deg is race spec, i can rev it to 8000rpm but symptons are loads of fuel getting drawn in,,,,,with not enough transfers to move it so gets spat back into a puddle in the bellow and is then flooding the engine. new kit,,,,,the old one will do on a sprinter lol

[Warkton Tornado No.1]

Inlet duration of 145° is about standard for the Indian produced kits & not excessive.

You suggested that you may have fitted the piston upside down, so that might be checked quickly via a borescope if you have access.

Most regular engine builders will completely disregard any cast in timing marks for ignition, other than utilising the arrow on the flywheel which they will look for when strobing, having first marked their own version of TDC & their desired firing point. Despite the reason given for adopting electronic ignitions, this Forum is testament to the un-reliability of the Indian produced ignitions. IMO you have an ignition problem & that can often be shown via a strobe because if - for instance - the ignition is breaking down as the RPM rises, it will be seen as the strobe will indicate a misfire.

[Adam_Winstone]

145 inlet is far from race spec, although the relationship of inlet to exhaust is very important as the extent that they communicate is surprising...

As Scooter Center once published in their well produced catalogue, typically inlet becomes poor if it exceeds 350 degrees less exhaust duration. In your case, inlet should not exceed 180 degrees (350 - 170).

The above sounds crazy but my own tuning of piston port motors suggests that it shows itself to be not too far out. I've proven this by running 176 inlet duration on my 240, then completely murdering it when increasing exhaust duration! Thankfully, I then brought this back to decent starting and running by fitting a new piston and taking duration back to 160 degrees. This relationship explains why Webster's inlet durations worked, as a result of his short exhaust durations.

Your 145 inlet is less than I run on many of my standard'ish motors with standard carbs. Some people would only consider 145 long because of today's tendency to extend exhaust durations for BHP figures on dynos.

My thoughts only... others will have different opinions.

PS - I like WT1's response... good info and possible ignition issue is why i suggested a trial with other flywheel. Lots of flywheels suffer air gap misfire problems and some tilt badly on tall woodruff keys.

[shamrockexpress]

There is no misfire what so ever, two different stators, keyway and flywheel feel tight and good fit, tried another coil/ht lead, its defo not carburation as i took an sh22 off a fully functioning engine and exactly same result as other 3 carbs i,ve tried.....really good compression on kickstart, height of inlet port is 21.5mm as opposed to a bored 175 LI cylinder inlet is 16mm high. i,m going to try this other cast 175 kit with all the same components of before this will then tell me if its the kits at fault.....i fell ive exhausted every other avenue.

All the above advice has been taken on board,,,,,,,this is a budget build as i want to get it off the bench as i,ve bigger fish to fry....lol
I will keep yous informed of my findings,,,,to date the one thing i,m sure about is i,ve F****D it up again.
All fun

[Adam_Winstone]

We've all been there.

[Warkton Tornado No.1]

Nowadays, as soon as you do anything to an engine, we are very lucky if we don’t take into account many things that are ‘mandatory’ to have a successful build

Pressure testing, compression measurement, squish optimisation, ignition checking etc etc are all standard procedures, but, reading this Forum, these days there’s no certainty that we can rely upon the quality of the fuel we buy! Not only can it be so often bought contaminated, who can tell with any certainty for what length of time it remains useable? The common belief may be about three months, but does that apply to when kept in a sealed jerry can or to a Lambretta fuel tank made with a bare steel internal surface?

Seriously, because I have to fuel up other devices such as garden tools & I rarely start any of my scooters due to other commitments, I am considering buying some Avgas from the local aerodrome simply to remove one variable. I think the shelf life is something like four years so, despite the extra cost & slight loss of power, it would be worth the investment for peace of mind

[shamrockexpress]

I did the standard home garage fuel test........poured a litre into a clear water bottle and left standing for a few hours, not scientific but no water at the bottom and clear other than the red 2 stroke. Reason for the test was when i took offthe carb bellow to empty out the excess spitback it always looked creamy/emulsified, the fuel was bought maybe 8 weeks ago super unleaded, the avanti engine was driven with no issues on the same tank 4 weeks ago!!!!!
So who knows not me anymore!!!! its driving me to the Drink

[Warkton Tornado No.1]

As you are adamant that ignition is not the problem & fuel quality seems to be an unlikely suspect* then there must be a reason for over-fuelling. I remain convinced that the inlet timing is not excessive, so have thought about how this problem may be occurring.

Presuming that the carburettor(s) are all functioning correctly - no float sticking/leaky float valve whilst subject to engine vibration - then upstream of the carburettor may be the issue.

IMO the OEM type bellows are barely adequate for purpose, though the Innocenti originals are a world apart from the Indian/dubious soft type. Theoretically, the CSA (Cross Surface Area) of the 22 mm size bellows should allow a larger bore carburettor to breath, so with one attached to a 30 mm VHB, I set out on many a test ride. Whenever I wanted some fruity acceleration, the engine would choke up & it took me ages to suss out why. On the stand, the engine would rev out cleanly & sounded good. However, under load, the soft bellows were actually collapsing, although, as it turns out, even the more rigid Innocenti bellows were a restriction on that particular engine.

I’m glad that I learnt this as it had to be seen to be believed. This lead to quite a bit of experimentation & I found that even with a rigid elbow on the carburettor with nothing else, the bike would choke up under load. The conclusion that I learnt was the shape of the carburettor air feed is not as important as the volume & that resulted in quite a bit of experimentation with alternative elbows/bellows etc.

If you haven’t already tried, what happens with no bellows connected to the engine?

* I have no idea as to whether modern fuel being hygroscopic means that water is absorbed within or remains separate. There appears to be DIY tests outlined on t’internet but I haven’t checked them out.

[shamrockexpress]

Ok everytime engine flooded and stopped i,d remove bellow empty fuel out (always trying out different size breathsweet filters on top). Next procedure to start engine again is keep bellow off kick over a dozen times with throttle open until motor starts again, its nessecarey to keep reving to stop it dying out even at fast idle when with NO bellow visibly petrol spitting out of carb until it literally running weak/fast until i connect bellow breathsweet again then ok to rev and slow off tick over a bit but wont take over reving is nessecarey for maybe 20/30 seconds by this time then floods out
i have this 197cc top end off now and all looks good,,,,,,so the only way forward is to put another top end on this sunday with all the same components to see if the 197 kit is at fault....will keep you posted.
thanks for now.
regards Damian

[Adam_Winstone]

I can't help but keep coming back to it sounding like the fuel leve6is too high in the float bowl as though needle is not sealing/seating correctly. I've had this happen as a result of needle length and because of vibration, often because of carb touching engine mount or cowling bolt head.

Something is certainly wrong and it sounds progressive, as though fuel level rising and flooding it.

I've also had progressive choking caused by a blocked standard exhaust..

[shamrockexpress]

Update,
Ok replaced 197 kit with cast iron 175 kit, SR piston and std indian exhaust.
Using the same carb,bellow breathe sweet, stator,cdi,flywheel, spark plug,
3 or 4 kicks with choke on and fired up no problem so kept on a fast tick over for five minutes slowing it off and it sat tking over for fifteen minutes until i stopped it.
Restarted first kick and after strobing the timing which was bang on, scooter is ready for a test run.

Conclusion is the indian 197 kit was the problem,,,,,,,i reckon port timings were out, Just my Unprofessional opinion........lol
Taking into account the piston skirt had been cut by 5mm this is likely to blame so if i come across a 65.6mm std piston i could always do more investigation , other than that its case closed...
thanks again gents for the mental support/info.