Derestricting my CB500

[pendulum]

I've decided to do Accelerated Access, as I don't fancy the 2 year restriction period. The bike's gutless from 45-50mph onwards and struggles to keep 70mph on some uphill A roads. I'll get my girlfriend's dad to ride to and from the test center. If I pass both first time, it's only cost me £90, and that's money well spent I think. I've got the use of the car in the meantime.

It's got an FI restrictor fitted. I've got the two correctly sized main jets from David Silver spares. I have not done anything like this before, but I want to have a go at de-restricting it myself. I've looked through the Haynes (which I don't find all that clear to be honest). I take it I remove the carbs. Can I just check it's the Float Chamber cover I remove to access the main jets? Haynes says I'll need a new gasket for that, oops, I take it I should order one of them. The float pin and all that - I don't touch any of that do I?

Any tips etc appreciated.
I may take pics along the way and post them here to make sure I'm doing it right and it might help others that come to do it in the future
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1998 CG125 (Sold) CB500 [+ Clio 172]
Usually_Wrong: I tend to fail more than pass. [Speaking about Theory Practice]
Usually_Wrong: im on unemployment at the moment

[P.addy]

No idea why a re-jet would have been done.

Just pull out restriction washers..

[cb1rocket]

it may well not need new main jets, worth checking however.

The restrictors are 2 plain disc with a smaller hole and are located between the carb and intake manifold. No need to dismantle the carbs other than take the float chamber off to check the main jet numbers.

[cb1rocket]

also a restricted CB500 should still do a decent 90mph uphill!

[GREENI3]

Gutless after 45 mph? Struggle to do 70 mph up a hill?
BS.

You must have a pretty crap cb to come out with those figures.

As for the restriction, just take the washers out.
I can't see why it would need a re-jet and unnecessary messing about with the carbs.

[pendulum]

Ok, cheers.

I did a bit of research and discovered the FI International usually change the jets to #125 size from #122 on the CB500. I've seen this mentioned in many different threads so trusted the info, but I will check the old ones, to see if they have indeed been changed.

If it was just a case of removing the washers, I think I'd be a bit more confident, maybe the jets I can manage too (we'll see ), but some threads mention other things get changed too when the bike gets restricted (like modified inlet rubbers, and a mod to limit the diaphragm slides, whatever they are!). How will I know if this has been done

Re: my bike's speed. I've seen people say they can get up to 100mph after a long run up on a restricted CB500. On a perfectly flat road, I am very lucky to finally reach an indicated 80mph, which probably equates to 75mph or less in real life. With a headwind or a hill, I have dropped down to below 70mph before despite having the throttle fully open. That's not much better than the 125cc I've come from. From stationary though, the bike's very quick. Perhaps I have another problem with the bike, I'm not sure, but because the bike is fine at the lower speeds, I've always just assumed the restrictor kit had restricted the bike more than it needed to. I guess if everything goes to plan I'll soon find out.

I'll start tomorrow.
____________________
1998 CG125 (Sold) CB500 [+ Clio 172]
Usually_Wrong: I tend to fail more than pass. [Speaking about Theory Practice]
Usually_Wrong: im on unemployment at the moment

[stinkwheel]

A genuine Honda restrictor kit alters the main jet diameter and has restricted inlet rubbers.

An FI kit has washers in the inlet and different main jets. So if it's an FI kit, you remove the washers and fit the standard (smaller) main jets.

I used to be able to get Mrs stinkwheels restricted CB500s up to about 90mph if I wrang its neck for long enough. Top gear may as well not have been there.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[pendulum]

I see, thanks. It's definitely an FI kit, it came with the red certificate. I'm going for one last ride and then I'll start work. Can you confirm that I'll definitely need the new Float Chamber cover gasket? I've read so many threads and none mention needing that at all, but I think I do?
____________________
1998 CG125 (Sold) CB500 [+ Clio 172]
Usually_Wrong: I tend to fail more than pass. [Speaking about Theory Practice]
Usually_Wrong: im on unemployment at the moment

[stinkwheel]

[pendulum]

Thanks, very helpful. And I'm glad I read that before I begun.
I've been putting it back all day (weather's been nice, I've been out riding ) but now is the time to go in the garage and start work.

Probably be back on here shortly with a problem
____________________
1998 CG125 (Sold) CB500 [+ Clio 172]
Usually_Wrong: I tend to fail more than pass. [Speaking about Theory Practice]
Usually_Wrong: im on unemployment at the moment

[stevo as b4]

This kind of post really confirms why i just don't like restricted to 33bhp bigger bikes. Having said that i've never even ridden one so wouldn't have a clue how they are to ride.

The CB500 is a pretty pokey bike in 58bhp guise relatively speaking. Certainely has more low-midrange drive than the ZX6R J i had at the same time, though the gearing probably confuses this somewhat. They will in ideal conditions put 120mph on the speedo, and have quite a noticable power band from 8000-10-500rpm. Sitting at 70-80mph and getting decent overtaking drive is normal.

While you bike is restricted, i don't really see how you can eliminate other possible issue's, but it is possible there is another factor reducing performance. The only time i've felt a lack of power with a CB500 is when it had a dirty airfilter and was running on 8month old stale fuel.

[Ingah]

Should do at least 90mph restricted - got mine to show me 100 indicated a couple of times with the proper Honda restriction kit fitted (#125 jets and inlet manifold washers). Slower top speeds indicate a separate problem / a bodged restriction method / other 'modification' (e.g. sprocket size).
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-- Ingah

[prawny1]

The fi kit doesn't require a re jet on cv carbs they have the same effect as limiting throttle /butterfly travel thats all (anything past 1/3 to 1/2 throttle has no effect on acceleration), the fuel metering is still done by the slide diaphragm and needle.

You should just need to pull the carbs out of the inlet manifols and pull the washers out with a hook or something.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[stinkwheel]

[pendulum]

I know you're right stinkwheel, I've read about the 125 jet upsizing in far too many places for it not to be true... however, I have just undone one of the float chambers, unscrewed the main jet, and on the side of it, as clear as day: 122

So, for whatever reason, it doesn't look like they've changed the jets on my bike when they did the restriction. I have however removed the two big restriction washers, one from each inlet.

Now I think I'm ready for the daunting task of trying to get the bike back together again

Edited because I meant to say "inlet"
____________________
1998 CG125 (Sold) CB500 [+ Clio 172]
Usually_Wrong: I tend to fail more than pass. [Speaking about Theory Practice]
Usually_Wrong: im on unemployment at the moment

[FantasticMrFo...]

Just a question as I've never fitted a restrictor kit before and intend on getting a CB500 when I pass my restricted licence.

Are there also washers restricting air flow on the exhaust manifold as well as the inlet or is it just the air in that the restrictor washers change?
____________________
Women are the cause of ALL accident's, If it isn't because one has run you off the road, it's because you have spent too long checking her out and driven up the arse of the car in front!
That or she's parked on an island, on a bend, leaving a gap even an anorexic couldn't fit through sideways!

[pendulum]

I think there's just two washers that do the work. If I am wrong, could someone tell me quick before I start putting the bike back together tonight
____________________
1998 CG125 (Sold) CB500 [+ Clio 172]
Usually_Wrong: I tend to fail more than pass. [Speaking about Theory Practice]
Usually_Wrong: im on unemployment at the moment

[FantasticMrFo...]

[GREENI3]

[stinkwheel]

[prawny1]

[Robby]

[prawny1]

Restrictor washers are not much more an impedance to air/fuel flow than the throttle butterfly itself with the throttle opened to a similar surface area, once the throttle butterfly opens wider than the restrictor hole it is doing nothing at all other than creating extra turbulance..

Again i will say these restrictors basicly make anything past 1/3- 1/2 throttle pointless, imo a restricted travel throttle tube would be a more practical way to restrict most bikes and would do away with the need for stripping half the bike down to fit them.

At the end of the day these kits are not legal anyway, it doesn't matter how you restrict the bike so long as it is actualy restricted, you are not required to present a "restriction certificate" either to police or insurance in the event of being pulled over or being in an accident, it is there job to prove the bikes power output if they suspect you of driving not in accordance with your licence.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[pendulum]

Job done, successfully Thanks for the help.

It took me a while but I do work slowly, I'd call it a three spanner job rather than the two Haynes give it, but for a newbie like myself it's challenging but doable
More importantly... what a difference it has made!
Where there was so little acceleration at middle/high revs before, now it just comes alive. It's like a completely different bike! It surprised me big time!

I shall book the next available Mod 1 slot in the morning!
____________________
1998 CG125 (Sold) CB500 [+ Clio 172]
Usually_Wrong: I tend to fail more than pass. [Speaking about Theory Practice]
Usually_Wrong: im on unemployment at the moment

[magicman-alex]

OK, was just about to take the restrictor washers out of the girlfriend's 1999 CB500 when I found this thread. Lucky - I had no idea about the possible change of jets. I thought it was just the washers.

Girlfriend lives about 300 miles away so only see her at weekends.

Here's the relevant portion of the certificate from an FI kit, which was fitted by a garage for the guy we bought the bike off. It has the garage's details on the certificate, but it was a Sunday so I couldn't get hold of the garage to confirm. Rather than having to take the bike apart twice or leave it in pieces while it's 300 miles away, I thought I'd leave it until I'd spoken to him.

I called the garage and spoke to the owner. He said the guy that does the restricting was on holiday, but said that he would NOT have changed the jets. He said in ten years of restricting bikes, they've never changed the jets.

So, judging from this thread. It looks like the job has been half-done by the garage? I suppose the good news is that I don't have to buy and replace a set of #122 jets.

I've only ridden the bike about three or four times. On a recent ride, it backfired. Could having the restriction washers fitted without the larger #125 jets cause this?