Carbs for a Monza Junior

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halfpast
Posts: 87
Joined: Sat Jul 18, 2015 5:52 pm

Carbs for a Monza Junior

Postby halfpast » Mon Jul 22, 2019 2:04 am

Looking to rebuild a MJ engine with a hotter cam and some head work. Any recommendations on what carbs would be a good fit? Thanks in advance.

Samurai
Posts: 137
Joined: Wed Nov 28, 2012 9:53 pm
Location: Somerset, U.K.

Re: Carbs for a Monza Junior

Postby Samurai » Thu Jul 25, 2019 6:16 am

No experience of a Monza Junior specifically, but if it has the inlet stub similar to my 175TS, then I've fitted. Dellorto PHBL22 straight on to it. The Dellortos have a huge range of adjustment, but therein lies their only downfall.

If you fit any carb that is non-standard and you can't get reliable data for a starting point with the setup, you'll essentially be your own development fuelling specialist. That can take up a lot of time and money on needles and jets before you get it spot on.

Ask me how I know . . . :roll:

halfpast
Posts: 87
Joined: Sat Jul 18, 2015 5:52 pm

Re: Carbs for a Monza Junior

Postby halfpast » Sun Jul 28, 2019 10:45 pm

Thank you!

halfpast
Posts: 87
Joined: Sat Jul 18, 2015 5:52 pm

Re: Carbs for a Monza Junior

Postby halfpast » Sun Dec 22, 2019 5:12 pm

Samurai, if you're still out there I have a question - it seems like the PHBL series carbs do not have a 'tickler'...are there any tricks to getting the carb primed before starting the bike?

Thanks in advance.

Bevel bob
Posts: 1042
Joined: Thu Apr 15, 2010 8:01 am
Location: Bromley Kent UK.

Re: Carbs for a Monza Junior

Postby Bevel bob » Sun Dec 22, 2019 8:20 pm

Lean the bike over to the opposite side (the right) to flood the float chamber.

Samurai
Posts: 137
Joined: Wed Nov 28, 2012 9:53 pm
Location: Somerset, U.K.

Re: Carbs for a Monza Junior

Postby Samurai » Sun Dec 22, 2019 9:20 pm

Hi, you're quite correct, the PHBL series have a 'normal' choke which you can choose to have lever or cable operated depending on the set-up ordered.

I have mine cable operated using the original air-controller handlebar lever. I find that from cold I use about 3/4 choke, about a quarter throttle and from TDC it normally fires first or second kick.

Correctly set up, I find that you'll need to let the bike warm up for a good 5 mins on slightly decreasing levels of choke till it will idle reliably without dying with the choke off.

If you look at some of my earlier posts you find the carb settings I've ended up using for my standard 175 TS, which will hopefully save you a while bunch of heartache and cash to get you in the right ballpark.

Hope this helps.

Jason.

halfpast
Posts: 87
Joined: Sat Jul 18, 2015 5:52 pm

Re: Carbs for a Monza Junior

Postby halfpast » Sun Dec 22, 2019 9:38 pm

The definitely helps! Thanks very much.

tweaky beast
Posts: 44
Joined: Tue Nov 08, 2016 1:55 am

Re: Carbs for a Monza Junior

Postby tweaky beast » Fri Sep 11, 2020 5:10 pm

I've fitted a Amal concentric MK1 624 to mine. Jets as per Burden's STD 24 mm carb. Very close to good. Made a little manifold . What can are you hoping to use.

ducwiz
Posts: 604
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: Carbs for a Monza Junior

Postby ducwiz » Sat Sep 12, 2020 2:15 pm

Hi, you're quite correct, the PHBL series have a 'normal' choke which you can choose to have lever or cable operated depending on the set-up ordered.


Contradiction - No. The modern Dell'Ortos have a tiny separate starter carb, not a 'normal' choke. Such device - a slide or butterfly valve - would mechanically restrict the air inlet. Instead, the starter carb operated by a tiny plunger or piston, and delivers an enriched mixture, independent of the main carb system. This is why one should not open the throttle during a cold start, but only lift the starter plunger.

Hans


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