Problem starting 172 malossi/phbh30

Please somebody help!
I have almost finished rebuilding a totally knackered '87 T5, replacing a dead polini 152 and si 20/20!! with brand spanking malossi 172 and PHBH 30mm Malossi kit all brought from SIP. Starts 1st kick with the si20/20 (main jet 122) but won’t do a thing with the PHBH. Carb supplied with the following; Malossi manifold, Pollini Rubber with 55 idle, 144 atomiser and 115 main.
I have tried with/without air filter and adjusted jets 'till my finger’s fell off[:rotate:]
Is there a known problem eg. the carb sitting to high/tilted or the jets to small?
Please help, the scoot looks top doller apart from the poxy engine.[:drink:]


Cheers Dylan, motor screamed like good 'un. The slide is a 40 and no i did’nt spec the jets from SIP, thats how it came. I will try and get a bigger main jet as there seems to be very little juice getting to the barrel, the plug is as dry as a bone.

Thanks again,
Dave [:look:]

Hi Dave, just borrowing your thread for a mo but if Dylan reads this, I fitted a Malossi 172 to my T5 and also a Cosa clutch as recommended by those good folks at SIP with a regular 24/24 and a sito plus but the clutch seems to make no difference to top end at all. I put in the 122 main jet that came with the Mal. whats your thoughts on the suitability of the set up. Ive also never messed with the spark angle, what will advancing the angle do and what shouldn i set it to bearing in mind i’m no mechanic and relatively new to scooter maintenance. Cheers in advance. Any other views also welcome its just i see a lot of good advice mailed in by Dylan. :shoot1:[:dance3:]

Cheers Dylan, top boy!
Blew it out with an air gun, slung it round the garage a couple of times and eureaka, the bastard works. Now ALL i have to do is get it set up right, hope my missus don’t want any DIY doing for the next 6 months[:smile:]


Cheers for the superfast reply Dylan, the clutch is a 21 tooth so differs from the conventional 20 tooth setup on a T5, I wasn’t expecting earth shattering performance as it is smoother and slightly quicker through the gears but i did expect an extra 3-5 mph on top from what i had heard from SIPwhen matched with the 172.
Got myself a bit lost on the plug thing and was really asking about timing settings and what advancing the timing might achieve.
As for the bearings i haven’t replaced any apart from the small end bearing that came with the Mal. but am now getting quite a lot of vibration through the bike just before engine scream but goes at highest revs, think a rebuild might be in order but will have to wait til rally season is over as i can’t be done with running it in again so soon especially as IOW looms so close. :shoot1:[:dance3:]

Yes, the jets that those carbs with almost always need changing. That’s how they come from the manufacturers and as these carbs are used for many different purposes they will almost always be unsuitable for your set-up.


Dylan or anybody else that can help,
Still no luck, have tried a 125, 128 and 130 main jet and a X2/X3 needle but still nothing. There is just no fuel getting to the engine.
WHAT THE **** AM I DOING WRONG[:bounce:]