High revving

[royblackburn1@btinternet.]

Hi all, started my twin up warmed it up to run on tick over set off for about half a mile and had to stop at a junction,the engine was revving high I had to pull over and let it die down prior to setting off on the run I could hear the throttles snapping shut air screws are one and half turns out and exhausts at tick over seem to have same pressure coming out,any ideas please. Roy

[chaz]

i would have thought high revving would be a cable sticking or an air leak.
if the sides click down are they actually right down or sat slightly high

[Mike Farmer]

 

Maybe not retarding. My Beemer R80(sorry don't usually swear on here) was a horror for that same thing.


Mike

[royblackburn1@btinternet.]

Thanks guys but it was the throttle valve sticking and a air leak, sorted the throttle valve out but will get a new O ring, I thought the O ring was thin when I replaced it mine always distort when the carb is took off might not be an original from amal. Roy

[royblackburn1@btinternet.]

Hi all, well every thing was alright but the high revving is back when going to change gear or at a junction I let it die down then carry on, I am now thinking it might be a float problem how do you check the float level in a concentric carb, thanks Roy

[Caulky]

After removing the float bowl, press lightly on the float tang, with a small screwdriver/scriber.
The float should sit .080" below the bowl.
If you have a 'stay-up' float its easy to adjust the level.
Use an aluminium, viton tipped float needle.

[TTJOHN]

Float level can be the cause for over reving, when it's too low usually, if you have a concentric on there with the drain screw at the bottom it's fairly easy to get another plug or cork stick a hole in it to take a length of small bore tube, that way you can see the level quite easily and make necessary adjustments.

TTJohn

[bikerbob]

If the flange bolts are too tight it can cause distortion and the throttle valve could stick they do not need to be very tight.

[royblackburn1@btinternet.]

Thanks for the replies, on stripping the carb down found that a throttle valve was sticking don't know why when I last had the problem I lightly sanded the throttle valve down and it moved freely and flange nuts not over tightened, decided to refurb  another carb.thanks Roy 

[chaz]

have you got the correct or enough insulating plates/gaskets fitted?
they are SRBP to stop the heat distorting the carb slide?

I have heard the newer anodized slides hold their shape better , we use it on ally parts subject to heat and cold effects on train brakes.

[TTJOHN]

have you got the correct or enough insulating plates/gaskets fitted?
they are SRBP to stop the heat distorting the carb slide?

I have heard the newer anodized slides hold their shape better , we use it on ally parts subject to heat and cold effects on train brakes.

I often wondered why trains never run in cold weather. 

[chaz]

take exception to that remark John

its not a problem with the brakes, its down to the rail companies and their preparations and maintainance.
Our brakes are used from the Russian border  down to Vietnam I think temperature variation of around 100degrees. https://upload.wikimedia.org/wikipedia/commons/4/4a/Rail_map_of_PRC.svg

[EDDIE SIMPSON]

train brakes consist of 2 friction pads squeezed together on a disc by a pneumatic caliper. no pistons or slides involved. unless in valves . high speed braking is controlled by traction motors - regen braking.
in frozen weather most people leave the car at home and catch the train instead.

[chaz]

sorry Eddie
our brakes dont use pads they use shoes and work on the curved surface, we pride our selves in the valves having pistons pulsing up and down many millions of times during the life of the unit. the units come back in after 5 years and are stripped and parts replaced as needed.
they are vacuum brakes , the brakes are held off by vacuum, should there be a leak in the system the brake shoes drop stopping the train.
after 40 years making the various brake systems , machining to assembly and test, being a 100 year old company that was taken over by the Germans as the only way to get the patent.
we are currently proving out and advertising the next generation of brake valve.

[EDDIE SIMPSON]

We call these brake blocks and used as low speed and parking brakes on a power car. Common on feightbut not so  passenger trains.our 373 s use them and the cylinders have a ratchet and spring which keeps the brake on when the air bleeds off.