Single carb on Mastiff AGAIN!

[breakwellmz]

I know it`s an old one but....
..I`ve got a PUMPER CV 40mm carb that i have hopefully sorted out a not too difficult way of attaching it to my Mastiff via a Yamaha manifold, we shall see!

https://www.ebay.co.uk/itm/Carburetor-C ... 2749.l2649

[breakwellmz]

Late night teaser over here are the bits n pieces - Grizzly(?)manifold, adaptor plate, extra pair of rubber manifolds, CV pumper carb.(Note how much more compact it is than than a standard one)

[breakwellmz]

The Grizzly manifold ports have closer spacing than the MZ head by about half an inch so the extra pair of head to carb adaptors, short lengths of tube, and the ally plate should sort that.

[droy]

Yes use the shortest (lowest) carb you can - there is very little room under the tank. The tank was formed (check the 3 inch round spot under the tank) so the stock carb(s) top can fit. I tried to use a 1/2 thick manifold extender plate that the Raptor 660 guys us to gain some manifold length and it caused tank/carb top interface issue.

[breakwellmz]

Hi.

Thanks for that.
Actually i think it must be a Raptor manifold i`m using as the Grizzly is a 4-valve head isn`t it?
Did the 1/2" manifold extender make any noticeable difference to your Raptor?

Cheers.

[droy]

I'm actually a Skorpion guy but using Raptor parts - most of the top end is the same, rod, cylinder, head. I actually just started a project with a Raptor header on my Skorpion! Raptor parts are all over the place here in the US!

The rubber manifolds on the Skorpion and Raptor are the same - as you know that metal manifold you have is for the late 1998 to 2003 Grizzly which is a 4 valve head (same as the 1990-1995 xt 600).

haven't ridden with the extender yet - still snowy here!

[ralf]

Please keep the forum informed on your progress. There must be lots of Skorpion owners like me who would love to find a successful single carb conversion sorted out. It's mainly the manifold that's the issue.

[DAVID THOMPSON]

me to i am not into go fast mode any more ...just want it to run nice'
dave 97 traveller in nice shape except the carbs are a pain

[breakwellmz]

Hi.
Will keep you updated.
Yamaha don`t help matters by swapping around the port shapes between XTZ660 and Grizzly 660 heads as you can see here - Why?

[grrant1058]

Hello BreakwellMZ,

Indeed that manifold you have is from a 660 Grizzly. I have used one of those on my 660 Tour, but it did take a fair bit of fiddling, welding etc. The biggest issue is the inlet ports are reversed so the manifold has to be fitted wrong way around ( "upside down" ) and the bolt holes are different. PLUS, turn the manifold upside down and the angle of the carb is all wrong.

What is required to make this work is: -

1/ Cut the mounting face off the manifold and replace it with a new mounting plate at a different angle so the carb clears A/ the starter motor and B/ the fuel tank. In the image attached you can see I have not yet drilled all the mounting holes.

2/ As the bolt holes for the Grizzly manifold don't line up, make up an adaptor plate (similar to what you have pictured) that bolts to the existing inlet manifold mounting holes on the head. This plate will need to have bolts coming out so the modified manifold can bolt to the adaptor plate.

3/ Bolt the modified manifold to the adaptor plate on the head and good to.

I have used a 39mm Keihin FCR pumper flat slide from a WR450 Yamaha. Fuel economy is about the same. Starts easy, idles perfect and throttle response is so much better. Pops the front wheel easy as pie, now that wasn't necessarily my goal, I just wanted to get rid of those old outdated carbs and use the latest and best technology in an easy to use/ tune single carb. I have the identical carb on my DR650. Totally transformed that bike and I now have over 100,000 km's on that carb on my DR, so they are a long lasting option. Jettings specs identical to my DR. Check out all the specs here. http://mxrob.com/

Cheers - Ron

[breakwellmz]

Hi.

Due to not having access to a TIG welder these days i`ve used a rubber manifold from a Honda XR650 between Grizzly manifold and my carb which is angled enough to bring the carb horizontal, a mate will turn me up a simple adaptor ring to join the two.
I made my adaptor plate out of 10mm ally plate, a couple of hole-saws and a dremel, quite satisfying really.
Waiting on my pair of rubber manifolds to arrive before i can proceed.

Cheers

[grrant1058]

Make sure you post up an image of how you are doing this. Sounds like you are using the two original rubber inlet manifolds and making an adaptor between them and the Grizzly manifold??

[breakwellmz]

That i will!
Yes that`s right but using two pairs of the mini manifolds flipped around to get the centre-to-centre spacing difference sorted between heads.It makes the inlet tract longer than original but so did these Bikeworx manifolds (second photo) -
Very tempted to try this out with my new carb just to see how it goes (first photo) -

[breakwellmz]

Hi.

Took the original carbs off today and couldn`t help but put my new carb into the right-hand rubber `manifold`where it was a perfect fit!
The MZ enricherer is also a straight fit and the throttle cable outer retainers only needed the lugs cutting off and the holes opening out to 6mm clearance (for the adjusters) for the cables to function as they should.
I am now even more inclined to see how it runs in this form with the left-hand carb port blanked off.
I was surprised how small the link port is between the left and right inlet ports proper - an oval shape of perhaps only 8mm x 12mm.
I think i shall try out this setup with this link port both open and blanked off.

Cheers

[breakwellmz]

The beast lives!!
After making a temporary blank for the left hand carb port and connecting cables and fuel line, it started up promptly with a bit of choke and settled down to a reliable idle.
After a little warming up throttle response from idle feels good and it reminded of my DR350 engined Beta Alp as i rode it slowly away from my garage, time to sort out an air filter.
Can anyone tell me the best way to remove the air filter box please?

Cheers