sooty plug on twin

Jon · Post by **Jon** » Sun Sep 02, 2012 11:35 pm

got a little Issue with the CD185T Benly... I can't get it to idle properly...It is either revving up or it idles lumpily briefly then dies. The pilot screw seems to do very little.

I naturally assumed a carb issue so cleaned all passages with switch cleaner and a wire, cleaned the pilot jet, ensured the inlet flange was square and the rubber seal was in place, checked float levels tried the float up and down from factory settings...Basically the carb's fine.

It's timed up spot on. The advance retard is good and working.

Benlys use a wasted spark, single coil single points system. They have one carb, one inlet manifold and one condenser. At any revs above idle it runs faultlessly. It pulls hard and feels strong and clean.

...And one plug is clean as a whistle...very light brown insulator, clean electrode, and one is black sooty...

it can't be the points, the coil, the carb or the manifold because any fault there would be on both plugs as all those components are shared. it shouldn't be the plug lead or plug...Ive swapped the plugs and the lead would fail as revs rose plus at idle you'd see arcing...

So... would a tight valve make a plug sooty?

Jon · Post by **Jon** » Mon Sep 03, 2012 1:15 am

Having read up on it...It might be a tight valve causing low compression one one side. Still doesn't explain why the carb mixture adjustment seems to do very little though....

Oh, one more thing. If you rev the motor it'll drop back to almost the point of stall then pick up to a fast idle. the fast idle feels like it's on the slide/needle rather than the pilot jet circuit...

Still feels carby but how many times have I been tricked by stuff like this...

danbennett2891 · Post by **danbennett2891** » Mon Sep 03, 2012 6:42 am

It helps to use people as a sounding bord in these situations

If the mixture in on one cyl is fine and sooty in the other then the carb is fine. There is something differnt between cylinders. However you have to consider that the good cylinder could be the broken one! Personally I would do your valves and check your compression too.

Is there any way you could have aim air leak I'm your good cyl. This would make the mixture right for that and bad for the other.

Proper head skratcher

ayjay · Post by **ayjay** » Tue Sep 04, 2012 9:28 pm

sell it and buy a c90 ,or find a forum for that bike

Post by **davebike** » Wed Sep 05, 2012 7:45 am

I would check the valve clearances NOW sounds like a tight valve and those engines with little valves burn them easily! so check the clearances and then if you can a compression test
Ok CD/CM 125/200 wasn't that bad it was the CB125 twins the eat valves !!

Dave

Jon · Post by **Jon** » Mon Sep 10, 2012 1:19 am

Seems I haven't been getting notifications but thanks for the input chaps...Apart from AJay!...I already have a Cub wassock! i got the Benly because a lot of my journeys are 25 to 70 milers and at 50 mph the Cub is less economical than the benly and is working too hard in my opinion...

Anyway...I just couldn't be arsed with removing the carb every bloody day to try some other tweak or 'fix' so I splashed out £60 for a Chinese replica of the Keihin PD... ~One for a CM. Other than the choke mechanism being on the carb rather than cable operated, the same carb.

I think I found the idle fault... The new carb works great but while I was draining the old carb's float chamber (I inverted it over the petrol tank rather than undo the float chamber yet again) I noticed petrol coming OUT of the threaded hole which supports the choke cable bracket. The screw that holds the bracket in place was clearly new and had been hacksawn to length and it looks like originally the screw was too long, broke through the inner wall and created an air leak plus a high spot where the slide could get hung up on. Whether I can be arsed to put the oil carb back on after repairing it is another matter seeing as it is running so well...

Is it still sooty on one plug...Dunno...haven't looked but I did the tappets and also removed the inlet manifold and cleaned and flatted all the mating surfaces by rubbing onto glass paper sitting on toughened sheet glass and with the new carb as well it idles very smoothly at very low revs now.
A couple of jet tweaks to go, when hot it'll stumble just off idle and this little 185 has enough oomph to hum along at 40 plus with the throttle literally JUST cracked open off shut in top so the pilot jet/needle is a bit rich around there. Cracking little bike though and I reckon better than the 200 Benly, better built certainly...lots more forged alloy and so on...Nice!

danbennett2891 · Post by **danbennett2891** » Mon Sep 10, 2012 12:24 pm

when i saw you posting before about the Benly i looked it up and thought i could do with one of those. i have been spoiled by the cub with the parts so easily available. i have just got the nx650 back on the road but i am not feeling it anymore i might sell it and get something like that.

Jon · Post by **Jon** » Mon Sep 10, 2012 12:47 pm

danbennett2891 wrote:when i saw you posting before about the Benly i looked it up and thought i could do with one of those. i have been spoiled by the cub with the parts so easily available. i have just got the nx650 back on the road but i am not feeling it anymore i might sell it and get something like that.

They are vastly under-rated... I am gaining huge respect for them. I think 360 degree parallel twins are the best engine configuration possible for a motorbike. the 185T will pull smoothly from walking pace to 75 mph in top and is extremely comfortable...

danbennett2891 · Post by **danbennett2891** » Mon Sep 10, 2012 1:00 pm

a parallel twin does make so much sense. v-twins have a nice clip clop sound but i do find that you get a problem with fuel draw through a single carb because of the uneven times between cylinders. my nx650 is a single but it is too agressive and has a problem with occasionally dropping a spark at idle. because it is a single it just stops dead in its tracks. straight two does make alot of sense. the only thing that stops my buying one right is my size. i would like the exact same bike just scaled up by 1.5x engine frame the lot. it is commical to see me on a c90 but that is half the fun, riding a bike made for a 10st chinese bloke! i have a kawasaki vn800 but again it is too small for me, my legs are all cramped.

this is the problem with buying older bikes, you cant just turn up at a dealers and see what fits!

Jon · Post by **Jon** » Mon Sep 10, 2012 1:08 pm

danbennett2891 wrote: the only thing that stops my buying one right is my size. i would like the exact same bike just scaled up by 1.5x engine frame the lot. it is commical to see me on a c90 but that is half the fun, riding a bike made for a 10st chinese bloke! i have a kawasaki vn800 but again it is too small for me, my legs are all cramped.

Benlys work on a different older principle size wise. they actually fit people. when you sit on a Benly, your feet sit flat on the ground and your knees are bent. Modern bikes are generally much taller. the advantage is you can muscle and hoof a low bike around in pretty much any conditions from gloopy mud to snow.

Benlys have little to do will cool or style and everything to do with lasting a really long time and getting you places with utter reliabilty...cub values in other words!

They are proper Hondas, designed in every respect to work as efficiently as possible

C90Club.co.uk

sooty plug on twin

sooty plug on twin

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