Request for advice - Rapide 276 Carburettors

[Mark Fisher]

carb issues

Stuart,did the cable break at the carb end or the bar end. If it broke at the carb end, where is the nipple? If the engine ate it then ther could be some damage... I hope not, but it seems odd that everything was fine before and now it is not. Having said that my cables usually break off at the bar end (twistgrip).
good luck.
mark

 

[Comet Rider]

Jet blocks

Hi Stuart,

Don't remove the jet blocks, as it messes up the interferance fit arround the pilot passages (dont ask how I know). it would be far better to ultrasonically clean them, as I do.

I use a dilute solution of B&Q brick and patio cleaner, then a session in water to remove the cleaner, then a final long session in either thinners or MEK (Volatile solvent cleaner)

I do this on all our bikes once a year, and we no longer seem to have problems.

Cheers
Neil

 

[BlackLightning998]

Thanks Neil - so how did you find that out?

Hi Neil,

Many thanks for the tip - I was going to follow the KTB tip and immerse the whole carb in warm water to release the jet block (having already tried it on a spare carb I have). Do you still vote no?

So how did you find that B&Q patio cleaner does the job then - that's an interesting one?

If I can find someone to ultrasonically clean them, do I have to then do the rest of the cleaning regime, I have a friend who is a tame jeweller and might get him to allow me to put them in the "rough" unltrasonic cleaner (not fine stuff).

Cheers

Stuart

Hi Stuart,

Don't remove the jet blocks, as it messes up the interferance fit arround the pilot passages (dont ask how I know). it would be far better to ultrasonically clean them, as I do.

I use a dilute solution of B&Q brick and patio cleaner, then a session in water to remove the cleaner, then a final long session in either thinners or MEK (Volatile solvent cleaner)

I do this on all our bikes once a year, and we no longer seem to have problems.

Cheers
Neil

 

[BlackLightning998]

Hi Mark - nice to hear from you...

Hi Mark,

Snapped clean at the throttle bar end - ni nipple in the engine luckily.

Cheers

Stuart

PS I think I may have been kidding myself that all was fine before the throttle cable broke - it ran OK but when I have looked through my spares box and pulled out the NGL: BP6ES that was in the bike up to about 200 miles ago it is sooty and black as well - so I think it has been running rich all the time I've had it - just the cable snap and replacement with a lovely smooth new cable has thrown it over the edge and caused it to run lumpy or on one cylinder.

S

Stuart,did the cable break at the carb end or the bar end. If it broke at the carb end, where is the nipple? If the engine ate it then ther could be some damage... I hope not, but it seems odd that everything was fine before and now it is not. Having said that my cables usually break off at the bar end (twistgrip).
good luck.
mark

 

[Comet Rider]

Ultrasonic Cleaning

Hi Stuart,

I bought a cheapo ultrasonic cleaner off ebay (cost me £30). What i do is to put the cleaning solution into a beaker and then put the carb into the solution (make sure the solution is deep enough to cover everything) then place the beaker into the water sitting in the u/sonic cleaner. This way the cleaner stays nice and clean, with no contamination, and the cleaning solution can be filtered through a coffee filter if necessary.

Cheers
Neil

PS
I was using a comercial cleaner called FETCH, but when I left that job, I couldnt get it anymore, and the patio cleaner was sudgested as an alternative...

 

[BlackLightning998]

Fingers crossed I think we've fixed it......

Evening All,

I've been using the Forum as well as JTAN to try and sort out my over rich front cylinder post changing the throttle cable when it snapped.

Originally I had thought the problem was caused by the new cable over the 25 years old sticky one - but eventually I came to the conclusion that the bike had been running rich since I had it - the cable had merely tipped the problem over the edge.

I thought I would drop people an update - hopefully it's not too early to claim success but I have just returned from 75 miles.

As was eventually suggested during a very interesting conversation with Andy Smith who's something of a fuels specialist I ordered some parts from Burlen Fuel Systems (couldn't have been easier on the web) and I changed the needle for a new one (set at middle notch), new needle jet (106 after some research which I think is Rapide Standard) and new main jet (170, Rapide Standard) in the front carb.

She ran superbly tonight, I pulled the plug at 5, 30 and 75 miles – sooty around the outside and nice and even clean/tan coloured in the centre electrode. It stayed clean throughout the run and the bike ran very well.

That persistent and annoying flutter/hesitation that I have had since I got the bike has gone.

She ran fine from 30mph in top through to about 95 when she began to run out of steam – slightly earlier that she used to. I tried closing the air lever on the front cylinder at various throttle openings – at all but wide open the air levers began to choke the engine and she fluffed – clearing again when I opened the air lever. At wide open throttle setting the air lever made no difference at all.

The cylinders are not quite balanced – I think she is leading with the rear cylinder slightly and not running quite as smoothly as I know I will be able to get her with a little work on fine tuning.

The really good news I think is that I have actually traced a problem that has been there since I got the bike and it is now fixed.

The needle that came out is visibly worn under a magnifying glass – and you can feel it when you run your nail over the surface too.

So a great process of elimination using all the suggestions from both JTAN and the VOC Forum subscribers, working my way through them checking each one and finally settling on new parts for the carb. Fingers crossed. I am getting ready to ride to York on Saturday for the Bill Hancock Riders Rally so 500 miles in the day should give me a good opportunity to test the bike.

Need to fit the new TT100 rear tyre befofe that though.

Thanks so much to everyone who made suggestions, delved into their experience for me and generally offered support and advice.

A hugely frustrating couple of weeks with some trial and error too - I have learnt so much along the way, feel now a bit of a Spark Plug expert (anorak) and what a wonderful feeling of elation when I pulled the plug at 75 miles and it was clean.

Thanks and Regards

Stuart Metcalfe

 

[methamon]

Hi John,

I wouldn't have thought I have done any lasting damage running slowly for 10 miles on one cylinder do you?

I know now that removing the plug is the preferred option when doing this next time though.

Thanks for taking time to reply - perplexing....

Stuart

A word of warning about running a twin on one pot with the other plug out. I once started my Boxer twin with one plug out..........and the HT lead dangling in the proximity of the plug hole. All was rosy briefly until I was suddenly enveloped in a fireball about 1 yard diameter due to the cloud of petrol vapour igniting. The fireball show was quite animated and fed regular charges of fresh fuel to maintain the inferno. As i was standing adjacent to the bike at the time I was able to relocate sharpishly & cut the engine. Following that the plug lead was still on fire but I quickly put it out and all that was hurt was my pride. You can see that things could have been devastatingly different.

Regards Methamon