No 4th gear!

[Billy BigWanger]

Hi, I will start by saying Im a newbie as far as Tuning goes so you may need to dumb it down a bit for me

Some time ago I picked up a complete engine that was running, I was gona strip downetc when had time.

But have had to stick in my GP because of major malfunction.

Its got a few issues but gets me from A 2 B, the main issues are Gearing. 4th gear is useless except down hills, and pulling away in first can cause problems if I give it too much juice (wants to die), In first its sluggish till its reaches mid revs, then just takes off (real kick in pants)and flys thru 1st 2nd and 3rd.

Tested her up hills, will fly up so long as the revs are there, back off the throttle then open her up and will struggle, causing me to drop down a gear (or 2) to get revs back up.

So what do I need to look at first?
Im unsure of exactly what the engine is, Told its a 196 built on a li150, ported, fresco, 30phbh, suzuki piston, yam crank. Any more details will supply if can

Cheers
Billy

[Knowledge]

It sounds over geared to me. I don't suppose you know what gearbox it is, do you?

If you have alook under the chaincase, I suspect you'll find that it has a larger than normal front sprocket. I'd think about running it with a 15 tooth front sprocket as a good starting point.

If it already has a 15 tooth front sprocket, I would suspect some over porting or poor carburation

[Skar]

Spec suggests it's a reasonably built motor but from what you have said maybe it's a bit revvier than what you are used to? Thrash it a bit and keep it in the powerband, don't expect torque in 4th!

[Billy BigWanger]

Cheers.
Will check on front sprocket, and report back.
The engine has been around a while so could be carburation. I suspect porting was done fairly well in first place (engraved signature underside of inlet manifold) but that dosnt mean someone hasnt had a go since
"don't expect torque in 4th!" I wish it had something! Anything other than downhill and it will slow down in 4th no matter how fast it was going in 3rd hit 4th and it starts slowing

[martinr]

sounds to rich try moving the clip on the carb needle up one notch this will lean it up a bit . if it works check the plug colour after a few rides

[sean brady scooters]

i,d suggest going back to the basics on this,firstly you need to know what gearbox/sprockets you have in there....(hope its not the vejay mk2 )
secondly look carefully at the top end and measure your port timings if poss......
you can then get some idea if the state of tune is compatable with the gearbox and pipe that your using.....etc

[Billy BigWanger]

Now I show my stupidity
Gearbox, is that not Li150, the whole lot is built on or around a 1965 Li150 crankcase, gearing albeit with a innocenti GP chaincase cover.
Sprocket teeth counting, will be getting on to that.
Port timings hmmm, that may take a little longer, will have to read up on a bit.
Martinr can give that a try as 5 mins to do and results should be immediate.

[Diablo]

If its an iron barrel with a suzuki piston these suffered from too much inlet timing which would explain a lot of the problems you are having. You have to live with it a bit to get the benifits of the jap piston. Also as said is probably overgeared.
Don't be afraid to run LI150 with 15/46 sprockets-its the same final drive ratio as GP200.
If your exhaust timing is long enough it will still pull a decent top speed.
A lot of people fit a 16t front sprocket and a stretched chain not realising it makes a pretty big difference.

[sean brady scooters]

typically the 190,s had inlet timings of 165 plus...
which combined with maybe a bad choice of gearbox and/or over geared......would explain most of your probs......