Shortest PHBH Carb Manifold?

[jonnyb]

Any suggestions as to the shortest reach PHBH Carb manifold for a piston port engine?

I've used the Mugello manifold on my last two engines and am looking for something as short as possible to give me more carb/pannel clearence for the filter, the MB downdraft one is an obvious choice and looks to give another 1cm or so clearence, is anyone using one or has any other suggestions?

I prefer the breathe sweet filter to my previous ram air/bellows arrangement but it is quite squished with the pannel on, I've been using it like this for some time with no trouble but would like to gain any extra space I can.

Any advice welcomed

[wack 63]

The easiest way I have found is to use a solid mount Malossi CDC manifold and lathe it down to a rubber mount type to whatever length you want.

[rosscla]

I got a Malossi one that's quite short

[Adam_Winstone]

The easiest way I have found is to use a solid mount Malossi CDC manifold and lathe it down to a rubber mount type to whatever length you want.

^... Exactly what I tend to do. I've done this to 3 for myself and 2 for a French mate (on here) so that there is plenty of room to fit a rubber mount PHBH with standard air hose and remote filter, without any modification to panel.

However, I started with a ScootRS manifold to shorten it for use with a solid mount 30mm PHBH, this being the setup that I've used on my long-stroke Muggy for a few thousand miles now. This arrangement fits nicely with remote filter on standard airhose, however, I did have to cut down the brass main jet holder so that it cleared the GP head cowling. I also had to do a considerable amount of work to open up the inside of the manifold to match the 30mm venturi.

^... on that note I'm shocked by how many dealers send out manifolds for a specific carb side that actually have a considerably smaller bore than the carb! I bought a manifold for a 36-38mm VHSB that had a 30mm bore, even though the dealer assured me that it was correct spec' for the larger carb and a manifold for a 30mm carb that had a 26mm bore!!!!!! CR@P!!!!! The best internal match manifolds that I've had are those that I've asked MB to match (credit where it is due), expensive but worth it unless you have correct tools, time and ability/skill to do it right.

Relating to your question.... the shorter the better but the angle needs to be suitable. The 2 places that I would consider for an off the shelf item would be MB and Readspeed, both of whom show what look to be suitable manifolds. Perhaps people on here can offer you some first-hand feedback on how these fit?

Good luck,

Adam

[camel]

ive shortened a solid mount old cdc 30mm manifold too to take the solid mount phbh,i can get a breathe sweet filter behind my sx panels no prob,i think this fuel throthing rumour with solid mounts is bollox,surely a rubber mount will "bounce" more

[Adam_Winstone]

^... yep, remember the days when everyone used the solid mount PHBHs, with TwoFour even selling them as 'the' Lambretta carb replacement! I've never had an issue with a solid mount on a road bike and I certainly like the additional panel clearance that getting rid of the rubber mount gives. That said, a short CDC manifold will still be fine with a rubber mount PHBH.

Adam

[jonnyb]

Thanks for all the advice guys

I did think about having my mugello manifold machined down but I don't want to be without the use of the lammy for a few days, my mate who does little jobs like that for me is great but can't be rushed! I'm going to give the mb or Readspeed manifold a try I think.....

[jonnyb]

Just for reference I had the Mugello manifold machined down for £20 at a local engineering firm, chap turned it around in a day for me.

I had to lengthen and tweak the fuel tap rod to go behind the carb but I've now got a breath sweet filter that is not crushed by the side panel and I'm much happier, I even needed to up the jetting a bit because of the increased air flow

[Darrell Taylor]

ive shortened a solid mount old cdc 30mm manifold too to take the solid mount phbh,i can get a breathe sweet filter behind my sx panels no prob,i think this fuel throthing rumour with solid mounts is bollox,surely a rubber mount will "bounce" more

definately not bollox
the bounce causes no problems at all unless it bounces onto a cowling/engine mount/tank and converts the bounce to vibration
had 3 scoots now on dyno with solid mounts that ive failed to jet in which weakened off uncontrollably at high rpm and when you try to hold the carb whilst its running up on the dyno you can see why as they vibrate your hand off ,had them with clear float bowls on and you can see the fuel frothing like crazy and the air fuel ratio goes off the scale

i think theres a few reasons why it wasnt as bigger problem in the past
more std,smoother running engines
soft std engine mounts
soft std shocks

upon stripping down the solid mount ive also found heavy float damage where theyve been vibrating on the bowl and body

[Knowledge]

I have been converting my manifolds to a flange rubber fitting. These carry the carb much closer to the frame, giving greater panel clearance. You just need some 10mm ali plate and a bit of time and effort to create the shape of the flange before getting your local ali welder to weld the flange onto the shortened manifold.

I have purcahsed these flange rubbers from the Far East.

http://www.ebay.co.uk/itm/220391537092? ... 1423.l2649

At less than £12 for a pair, the rubbers are a fraction of the price of those you can acquire from Allen's Performance. I've had this fitted for a season and a half without a split (but I always have a spare in the toolbox).

With a flange rubber, you can only have one-end of the rubber that might fall off, as the other end is bolted-on.