MB Reed Block for Piston Port.

[chris2470]

Anybody recently fitted one of the above?
I'm thinking about fitting one soon, mainly to try and limit the amount of fuel being spat out, so I would be interested in getting some feed back regarding any improvements made.

[Train Driver]

I had one fitted to my RT255 i was hoping to stop spit back, it didn't work.
It wasn't done at Mb but i spoke to mark who said it should have sorted it as the ones he has fitted have no spit back.
In hindsight he built the engine so i should have taken it back to him to fit
DON'T MIX AND MATCH YOUR TUNER/BUILDERS

[lozmondo]

I had one fitted by the bloke who tunes my engine. Has not stopped spit back, but has increased the MPG. still nees playing with as it doesn't rev like it did prior to fitting the reed block. may try a 28mm carb as opposed to the 24 Mikuni its running currently.

[coaster]

Here you go, this is my experience, I've cut and pasted this from another thread:

An update if anyone is interested. I bought one of the new MB 'short' reed manifolds with 6 petal reed block. Having read and studdied up a bit I descided to have a go with the dremel.

First I opened up the transfer feeds and raised the transfer ports from 115 to 125 and widened them a bit at the same time.



Then I matched the inlet to the manifold

Fins cut away to clear MB manifold.


Finally I cut a boost port running up from the top of the inlet to a point level with the top of the transfers which I understand should help counter some of the losses caused by the reads? Also, I left the exhaust at 170 and not very wide (45mm round circumference, approx 60%).I might play with that later.


This is the piston that came with the kit, already drilled and skirt shortened by 3mm by the previous owner, if it runs ok I will replace it with something better.


Having dived in and raised the transfers I was alarmed to hear that it's not a good idea to interfere with the top edge due to the ctitical shape and the high probability of screwing up the loop scavenging process. The advised way for an ameture is to use a packer and cut the corresponding ammount off the top of the barrel. Bell and Jennings both state that but I managed to miss it All porting done with a dremel, one carbide cutter and various grinding stones and sanding drums. I couldn't find much information about boost ports so just went with one central port about 15mm wideand maybe 10mm deep. I THINK I can widen it in the future if the top end is lacking?

Anyway, I decided to put it together and see what happened but I wasn't expecting very much, in fact I'd already picked up another cheap 225 barrel of ebay and left the cowlings off with expectation of stripping it all down again . Engine in, fuel on, choke on, 3rd kick and it started and setteld into a fast idle straight away using the same setup on the 30 PHBH as I had run on the previous 225 barrel. Slight tweak of the idle and mixture screws and off for a tentative blat round the lanes. I was very pleasantly suprised, very clean running, absolutelu NO spitback. I let it coast down to 15mph in top and then opened the throttle all the way expecting it to bog down, but it didn't it just slowly bulit up speed without any hesitation right up to about 50mph when the power kicked in quite hard. I think it might be a little weak yet and I didn't want to overdo it until I'd got some miles on it but all in all I'm well pleased and a little bit amazed

Comments and suggestions very welcome

[jason frost]

Done a few even have one on my own bike some pictures here http://www.facebook.com/media/set/?set= ... 0853187888

[Chris CSPE]

Regarding the engines with spit back, could it be that the pilot jet is to large ?

[coaster]

Regarding the engines with spit back, could it be that the pilot jet is to large ?

I'm sure that can be a factor but the spitback I'm refering to is caused by overlapping port timings ie the inlet and exhaust are open at the same time and the pulse from the exhaust blows the incomming charge back out of the carb. My Muggy 186 is quite bad in that respect

[mark]

that could be craigs problem

[Craig H]

Got a Mugello V4, anyone else with this kit had the same problems with spit back?getting a bit pissed off with it now....

[coaster]

Got a Mugello V4, anyone else with this kit had the same problems with spit back?getting a bit pissed off with it now....

Mines a Mk1 Craig but I don't suppose the port timmings are that much different. The spit back wasn't too much of a problem when I ran it with an Ancilotti, I had a remote filter on a 28/30 PWK and it ran fine except fort the common warm starting problem (fuel off before stopping thrick). BUT when I put the engine in the Jet for the C2C and stuck the JL3 on it the spit back made running with a filter impossible and with the filter removed the spat back oil mix covered the inside of the panel and runner, even the rear mudgaurd

I still think it's a blinding kit though, a reed valve will cure the spitback but it's not just a bolt on job, the cylinder will need to be re-worked otherwise you will loose a lot of top end.