Torn Keihin diaphragm

[Johannes]

Hi, tip toe-ing forward with this NC24 jigsaw. Had it running on the weekend, but noticed that the slider in the carb for cylinder #1 LHS rear not lifting. Removed diaphram cover and found split.

Diaphram looks like it is attached to the slider???

Anyone had experience of sourcing & changing these diaphragms???

I am assuming that they are the same carb setup as the NC30 (possibly slightly different jetting) so spares should be readily available???

Thanks.

[Drunkn Munky]

Different carbs to the NC30 although slides will fit but are shaped different

[hunter]

If you can get yourself a new one,Or even take one of a nc30 slide and follow these steps i'm sure you could fix it.
http://www.xs11.com/forum/showthread.php?t=33250

[Johannes]

Thanks for posts. Done a little research. Looks like NRP have diaphragms for £35 a pop however have come across a company in ohio called jbm industries that make aftermarket diaphragms for $19 each plus shipping of $26. I think that the NRP price is 'fitted'.

The JBM product looks like it would be the k-72-S just need to check some measurements on the slider first.

I'll update in the next few days. If anyone has used the jbm products before I'd be interested in hearing?

[Johannes]

OK JBM Diaphram $19.50 plus $26.00 postage. I'm only going to replace one at this stage so it's nip/tuck on price between JBM and NRP fitted option.

Have decided to go for NRP option. Have to send existing slide with torn diaphram minus needle to them they replace and send it back. If I were replacing more than one it would have made sense to go the JBM route.

[DAC]

Hi there,

NRP are really good, excellent choice. I had them fit a set of NC24 slides with new diaphragms and put them in my NC30 carbs as part of an HRC replica setup. NRP did a brilliant job and the slides have a really good feel when fitted. My view is that they offer a little more movement resistance but the originals were pretty poor so a comparison was always going to be difficult.

Regards,

Dave.

[Johannes]

Unfortunately, after 3 weeks of no feedback from NRP following sending the slide, i finally got through to them and they couldn't give me a timescale to fit one diaphragm! So I asked for my slide to be sent back with a replacement diaphragm, which they did and charged me the full price of supplying & fitting a diapragm. Am currently in conversation with NRP about this.

Managed to fit the diaphragm as follows. Note,this is the way it worked for me. I'm no expert but I've achieved a successful replacement through thought and care.

Firstly the diaphragm supplied by NRP is a 'soft-centred' unit not one of the ones with the firm doughnut in the centre. So you do not want to destroy the top ring on the slide! Many of the YouTube videos show the top ring being twisted or dremmelled off. DON'T do this.

Simply tear the old diaphragm off and away for the groove in between the two rings.

The new diaphragm will be too 'fat' to insert into to the groove so I opened the groove using a dremmel with a 38mm grinding/cutting disc in. Being careful not to cut into the slide body itself. I held the slide in a vice for this. Releasing and rotating the slide as required, until a consistently wider groove is created. I tested by fitting the diaphragm into the groove and noting where it was still a little too tight and then opening the groove a little more in these areas.

Once the inner part of the diaphragm sits comfortably in the groove ensure that it is in it's correct orientation with respect to the vacuum hole and that the slide is in it's correct orientation in the carb.

I then marked a line using a white wax crayon on the diaphragm and the slide. Removed the diaphragm and squirted Loctite Super Glue Gel in to the groove. Then I refitted the diaphragm into the groove ensuring that the white lines were aligned.

Then leave the gel to cure for a few hours and refit.

[Johannes]

Ok. all fitted and back together. Noticed that the NRP sourced diaphragm is a slightly thicker gauge and so offers more resistance to the slider than the Honda OEM diaphragms, as a result it is slower to lift than the other 3 on opening the throttle.

With hindsight I might have been better sourcing x4 diaphrams from the US. I could have done all 4 then.

Anyhow all working. Bike goes like stink if a little unbalanced!

[Neosophist]

sad to hear you having trobules, never used them before.

Aftermarket diaphrams are often different thicknesses, in hindsight, if the price is reasonable, getting 4 would have been good, there are a few guides on the net on how to fit the diaphrams.

balancing will mainly affect your idling.

good to know its runnign well though