MC5 400 Carburetors

[phats]

Hi all,

Im the owner of a 77' 400 MC5. I believe the carb body is worn, so im after a new replacement.

Could anyone tell me what carbs are meant to be on standard?
It has a Bing 54 on currently, not sure what size (38 maybe?)

Can i get a new Bing?
Or can i get a Mikuni?

If so could you please advise where?

Thanks!

[tomale]

go back to the home page and look under suppliers, there you should find Bing International. They can help you... Typically the replacement of a slide and the jet needle as well as the needle jet.. are all you need. but if you think you really need a new carb they should be able to help you with a new replacement...They will also be able to tell you what size carb and what is stock jetting.

As for a Mikuni, on my mc5 250 I have a mikuni on it and it works very well... not sure on the 400 It may work well or maybe not, I have a 440 maico with a mikuni on it and I am about to go back to a Bing.... you will have to ask around for that, not sure but do a search and you maybe able to find the jetting specs in a previous post...use the search button for that...  hope that helps

Thom Green,Still crazy after all these years!
76' 250 MC5 (orginal owner)74'
250 hare scrambler (project bike)

[Steve Minor]

Phats....Pretty sure the 400-MC5 came with a 38. I'm curious why you feel the entire carb needs to be replaced? That can be pretty pricey. Normally just the guts are freshened up....slides, floats, jets. How does the bike run now?

Steve Minor
Wilmington, NC

[phats]

The engines sweet as, however, when running develops an increasing tick-over.
My first thoughts were crank seals? However, no smoke is apparent.
I stripped the carb, the slide, floats.etc seem in good shape.

Also, not sure how there meant to be, but the actual carb bolts directly onto the engine and the drain bolt actually touches the crank cases?
I have a rubber manifold on one of my spare engines, not sure which is correct..

To start the bike as well, it requires full throttle, else it won't start. When youve tickled the carb, a large amount of petrol continues to flow out the overflow pipe (i know some is meant to come out, but this is a large amount).

If any of you have any ideas, they'd be much appreciated!

Thanks

[454MRW]

Once you have tickled the carb to the point that fuel trickles out of the overflow hose slightly, and started the engine, no fuel should continue to come out of the overflow hoses. It sounds like you have a float sticking situation, or the floats are set too high. That is probably why you need to hold the throttle open to start the bike. Mike

Michael R. Winter
I enjoy rebuilding and appreciating Pentons!
1974 250 HS Pentons-1980 KTM 175-400'S

[garrettccovington]

Phats
I got the manual from Bing and it is very helpfull.  Carbs are expensive, parts are resonable.

G

72 six-day
79 KTM MC80 250

[garrettccovington]

Phats
The bing manual covers every part of the Carb, Idle circuts, needle jets and main jet , plus the relationship corresponding to throttle twist.

I don't know what a tick over is.
G

72 six-day
79 KTM MC80 250

[phats]

Is it rare for the throttle bodies to become worn then?

And when i say tickover, i mean the idle revs are increasing by themselves.

Should i get a service kit for the carb?
Could anyone supply me with a working carb to try?

Or could it just be crank seals letting air in?

[Steve Minor]

Phats...in my opinion, you're sucking air from somewhere. You can search this message board and find some tricks to locate air leaks. I seem to recall the ignition side seal as a possible culprit.

As far as carb bodies wearing out, I suppose it's possible but usually just the "guts" need attention.

Steve Minor
Wilmington, NC

[marsattacks]

I am no expert but believe me if it is a crank seal the last thing you want is two-stroke runaway on a 400.  I had a very similar condition on a 250 that very quickly deteriorated.  Check the below link. I think if you are not racing and forbidden by the rules you could source a nice Lectron flat-slide carby (do some searches here for sizes mx/enduro).  Are you in the UK? I have a Lectron I could loan but shipping would be too expensive to make it work since I'm in U.S.  Good luck, John

http://www.pentonusa.org/forum/topic.asp?TOPIC_ID=10211&SearchTerms=insanity

Mars Attacks!

[phats]

I hope its not crank seals looking at that!! I don't think it's too hard to change them on a 400 if im correct? So might do it anyway.

So should i order a new carb? If so, a replacement bing, mikuni or lectron?

Or should i just do seals and buy a new slide for my bing?

Im not racing till April 11th so i have a bit of time.

Thanks!

[Steve Minor]

Phats...these are the settings I once got from Bing for my 77 400GS6. The prices are old.

1977 Penton 400cc GS6
Stock Jetting Specs @ sea level are:
44-051-185 Main Jet @ $4.38
45-120-3,22 Needle Jet @ $8.15
46-360-401 Jet Needle in position 2 from top @ $7.07
44-353-50 Idle Jet @ $11.72
54 Soft OHGK ( contains gaskets, o-rings, float needle, pivot pin and cable
grommet) @ $30.17
We accept Visa or MasterCard. You may order by email or call 800-309-2464.
Respectfully,
Fay




Steve Minor
Wilmington, NC

[phats]

Are those prices from the Bing agency Intl ?
Would it be worth changing the slide as well?

400's came fitted stock with a 38mm Bing 54 correct?

Chris

[Steve Minor]

My 77 400GS6 came stock with a Bing 38. I presume the MC5 did too. The prices shown in my previous email are from Bing Intl Agency, but are somewhat dated. They are very easy to work with and will reply to emails. The web site is http://www.bingcarburetor.com/

As for replacing the slide, they do wear out. If a "half-moon" worn spot is visible when you look into the throat, you might consider replacing it.

Steve Minor
Wilmington, NC

[brian kirby]

Yes, the Bing bodies do wear out, but more often its just the slide. In my opinion a 50 idle jet is too rich, it will run OK but if you stall it in warm weather it will not restart. I had a 50 to start with and I think I now have a 45 and I am going to go one more step down. Also if you do have to replace the Bing, dont waste your money on another Bing, get a Lectron. I've got nothing against Bings, but they are outrageously expensive and the Lectron works 100 times better.

Brian

'72 Berkshire