Bike won't rev after restrictors fitted

So I've had the carbs off and I've placed the restrictor washers in the inlet rubbers as per instructions(between the carb and the engine). The bike takes her time to start and requires the choke to start, after it's started I then twist the throttle and it won't go above 1500rpm if I give it any more throttle the bike will stall. I've done exactly the same process on my other cb500 and the runs perfectly as if the restrictors were not in.

Not had any personal experience with the restriction things, are there any jetting chances required perhaps?

That'd be my guess or possibly trapped pipes when the tank went back on?

I'm assuming it wasn't the OE kit as I believe that comes with replacement inlet rubbers & larger jets.

Beresford wrote:Air leak. Carb rubbers not sealing correctly. Sounds like.

I'll have another check but everything seems to be seated correctly. 

ANDYC wrote:Not had any personal experience with the restriction things, are there any jetting chances required perhaps?

Nope just the washers no rejetting required 

ashcroc wrote:That'd be my guess or possibly trapped pipes when the tank went back on?

I'm assuming it wasn't the OE kit as I believe that comes with replacement inlet rubbers & larger jets. 

It's the kickstart engineering one so it's just washer restriction and it's a 47hp restrictor not the old 33. Ill check the pipes when I get the chance but it also does this when the tank is off so I'm only using the fuel in the hose leading upto the carbs

Jameshambleton wrote:

Beresford wrote:Air leak. Carb rubbers not sealing correctly. Sounds like.

I'll have another check but everything seems to be seated correctly. 

ANDYC wrote:Not had any personal experience with the restriction things, are there any jetting chances required perhaps?

Nope just the washers no rejetting required 

ashcroc wrote:That'd be my guess or possibly trapped pipes when the tank went back on?

I'm assuming it wasn't the OE kit as I believe that comes with replacement inlet rubbers & larger jets. 

It's the kickstart engineering one so it's just washer restriction and it's a 47hp restrictor not the old 33. Ill check the pipes when I get the chance but it also does this when the tank is off so I'm only using the fuel in the hose leading upto the carbs

The 47 bhp restriction shouldn't make that much difference to a CB500!  So you've definatley done something else to break it ;)

I'm going to agree with beresford that it's probably an air leak around the carb rubbers.  Given that they are probably 20 year old (ish) rubber items they could be leaking anyway - dislodgeing them to install the restriction kit could have been the last straw!

Have you tried removing the restrictors to see if the problem's still there without them? As ET mentioned, removing the carb inlets to fit them could have caused the rubber to finally crack.

After removing the restrictors the bike started fine. I then refitted the restrictors and then it wouldn't start. I checked the plugs and they were very black. I got some new ones this morning, refitted the restrictors and boom started first touch of the switch

Haynes suggests:

Glad you got it going.

It might be worth keeping an eye on the plugs to see how the new ones fair though I'd expect it to run a bit leaner with the restrictors in.

ashcroc wrote:Glad you got it going.

It might be worth keeping an eye on the plugs to see how the new ones fair though I'd expect it to run a bit leaner with the restrictors in.

Yeah, I need to adjust it on both my cb5's but I'm not too sure on how to do it correctly yet so for now I'm gonna wait as they still run.

ashcroc wrote:Glad you got it going.

It might be worth keeping an eye on the plugs to see how the new ones fair though I'd expect it to run a bit leaner with the restrictors in

I'm suprised that there are no jetting changes, as the airflow is restricted it will have a knock on effect on the fuelling.
Same jet size to match a smaller volume of air will result in a rich mixture. Hence the sooted up plug pictured.
That is not taking into account the airspeed or pressure.