Re: Curvy Cold Starting Needs Running Start
 

If you have a multimeter it's worth checking the Spark plug caps.Set it on the 20k Ohm setting and test the caps.Stock they have a 5K ohm ceramic resistor in them.As they age the corrosion on the contact points inside and the resistor can increase the overall resistance.Once it starts going North of around 8K ohms they can cause all sorts of problems like bad starting/engine cutting out and misfiring and rev limiting.


https://i.imgur.com/Vh43D6p.jpg


They came in around 1980 ish but not long after Spark plug makers started fitting 5k Ohm resistors into the Spark plugs so this over complicated form of Spark plug cap is not even needed if using,"R" rated Resistor Spark plugs but motorcycle makers still fit them as standard.

I used to run both my old hondas with none resistor caps but with,"R" resistor Spark Plugs,no problems.

They were/are fitted as a filter to reduce the possibility of Back EMF(Electromotive Force) that can cause problems with other components in the Ignition system and not as some people believed as Radio suppression.

Even as recent as Yesterday my M8 came round to tell me his bought-from-new Triumph Street cup had just been fixed as it kept cutting out and it was Faulty Spark plug caps!! :O

Re: Curvy Cold Starting Needs Running Start
 

Do you mean the actual spark plugs or the rubbery shoe that goes over it? The plugs are pretty new but I did take the rear one out to inspect this evening. It looked quite sooted over (can see in the video I added today to the link below). Don’t know how to use my multimeter if I’m honest. Used it to check the battery and that’s about it...

Do you think it could be the plugs given their age (4/5 months)?


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Curvy Cold Starting Needs Running Start
 

I managed to get her going this evening to inspect the above.

The fuel pump and vacuum did not show any obvious external leaks. All hoses seemed sound too. And to be honest, the leak wasn’t there...the residue of fuel over the left side of the engine coming from that small hole was still visible from before, as well as some inside the valley between the cylinders, below the front carb if that makes sense. But no new, fresh leaking petrol. The only thing was the way the carbs were spraying (added video to below link).

possibly some worn needle seats or carb seals that allowed petrol to escape and overfill into the cylinders? I took the carbs off to change the seals and needles, seats etc..

I feel like this problem is starting to make sense to me...although still seems like a lot of work. There doesn’t seems to be a problem with the petcock as it was mentioned on the post that seeker posted that a torn membrane leak petrol externally. No leaking fuel hoses either. So must be inside the carbs...Does it make sense to you guys? Am I on the right track?

https://www.icloud.com/sharedalbum/#B0BJ0DiRHGNU4RA


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Re: Curvy Cold Starting Needs Running Start
 

I mean both the Spark plugs and the,"Rubbery Caps".The original Spark Plug caps are hard Plastic.Some people fit the Straight Race type Spark plug caps as they are much cheaper than the OEM ones,


https://i.ebayimg.com/images/g/jXwAA...f7/s-l1600.jpg

And as per my post even low mileage Spark plugs and Spark Plug caps can fail.It's not common but does happen hence the resistance tests.

Re: Curvy Cold Starting Needs Running Start
 

I couldn't get the videos to play in my Browser first time so I went back and downloaded them and then they would play.

It's almost definitely a carb issue and possible fuel in the engine oil/Hydro lock.

I had a similar issue on one of my Old Hondas with CV carbs.There's a set of circumstances whereby if the Floats have gone out-of-spec the Needle valves inside the carbs that they lift don't stop the fuel as it should when the the correct fuel height is reached.

Then if the engine happens to have been stopped with the inlet valves open and there is a fault with the Petcock as well fuel can drip into the engine and into the engine oil.As I said I had this happen and the engine would not turn over but I smelt fuel and when I took the oil filler cap off the stink was there and the oil was contaminated to hell.

If the engine had started I bet it would have been ruined in minutes.



As I already knew a lot about these carbs I took them off and cleaned and dressed the ends of the Float needle valves with some toothpaste(It's a tip in the Haynes for them) and reset the Float heights as they had gone out from 15.5mm from the perpendicular/Carb body which is the specs for the CX500.

I've not checked for the CV carbs in my SV as I've had no problems so far but will have a read later.




There's a nice blow-up here and it's parts 28/29 I'm talking about,

https://www.motorcyclespareparts.eu/...les/carburetor


This would also account for the fuel I saw bubbling at idle in the video.


Note:Once I had fixed the carbs I ran some cheap 20w50 engine oil in the engine for a few mins and then dumped it and then did it again and dumped it.Then used my proper engine oil.

Yes a bit of faffing about but for the cost of a cheap gallon of oil well worth it IMHO and had no problems with the engine and carbs after that for thousands of miles.

BTW.B&M Supermarkets are doing a 10w40 semi synthetic engine oil for £12.99 for 4 litres you can use as a flush.

https://www.bmstores.co.uk/products/...-oil-4l-334747

Curvy Cold Starting Needs Running Start
 

Firstly, thank you both for your invaluable input so far Seeker and Riff...keeping me on the right track with this

Appreciate you asking the tech.! To answer your question seeker, it was on the stand, yes. I’m just in the process of changing over the needles and seats. The seals came with the kit too, but are a load of crap as they main bowl gasket seal is not the same size and doesn’t sit flush, so keeping the old seal as that seems the better option. I have not changed the floats...should I?


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Curvy Cold Starting Needs Running Start
 

Cheers Riff.

I’m changing part 28 as we speak. 29 I didn’t get. Do you happen to know the correct needle height? I change it by adjusting the tab on the float, right?

I’ve cleaned the carbs with carb cleaner previously, don’t know how good of a job I did, as I’ve read some guys leave the jets soaking in carb cleaner for 3 days! I used carb cleaner spray and small bristles to clean the jet holes.

You say the engine would be ruined in minutes...well mine starts from time to time! And i rode to work and back a few times despite starting difficulties as shown in the vids... so I’m a bit lost as to what the actual diagnosis is...is it hydrolocked? The symptoms so far :
•oil smells of petrol
•petrol leaking from somewhere around the carbs and out of rear plug drain hole but not from the petcock or vacuum
•petrol spraying out of the piston valve that seeker’s tech said shouldn’t
•starting difficulties. Feels like it comes to a grinding holt when attempting to turn over. But after many attempts it eventually starts.

Currently am changing the carb needles and seats and some of the seals that came with the kit, although I’m pretty sure some of them are not right for my carbs which I’ll leave out

Will at some of that oil...I can use it in the bike right? Says is car oil...


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Re: Curvy Cold Starting Needs Running Start
 

Sooo...after stripping the carbs and trying to change the needles etc, I stripped a screw holding the needle seat in place. Long story short, couldn’t be arsed with this damned carb anymore and just ordered a second hand low miles one off eBay. Installed yesterday. No petrol smell. No obvious leak. No more petrol spray inside carb. Whoop!

Done as R1FF suggested, got some cheap 5L Halfords 10w40 oil to run through the engine and drained it. Repeat x3. Topped up with some fully synthetic Repsol oil to run with.

Feeling confident, rode to work this morning. However, now, it is backfiring and popping like nobody’s business at low revs (maybe high revs too but just cant hear it). If I let go of throttle, it eventually drops the revs and dies 🤦🏼*♂️ so have to sit at the lights with the throttle partially open and a load of popping from the exhaust...must be quite a sight. But I think it’s progress nonetheless!
Several things come to mind:
• change spark plugs
• carb adjustment screw set incorrectly and is running too lean (or rich?)
• carbs out of sync with engine (hope it’s not this as cannot do myself)
• carbs have vacuum leak
• overfilled oil a tad (would this cause backfiring?)

(Note: while tinkering I lost a small part from the choke lever when dismantling the handle. Now the choke keeps springing back. Doesn’t stay on. Will need to sort this but maybe is the culprit?)

What do you guys think? Is there a more obvious solution I’m not seeing?


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Re: Curvy Cold Starting Needs Running Start
 

However, now, it is backfiring and popping like nobody’s business at low revs (maybe high revs too but just cant hear it). If I let go of throttle, it eventually drops the revs and dies


The most common cause of problems after carb swaps/servicing is air-leaks being introduced so check again for them.Your above statement leads me to to this along with cable routing and of course Carb Balance check.



Also the 2nd hand carbs need some fuel cleaner in the fuel in case they are gummed up if you didn't strip and clean them.

As for Carb syncing it's not that hard with a Carbtune2,

https://www.carbtune.com/inst.html

I've done loads of carbs with mine.

Re: Curvy Cold Starting Needs Running Start
 

Thanks for the suggestions guys.

I put some Redex in the tank to clean it out and adjusted the pilot screw (hard to tell by how much as did it without taking them off) and tightened the idle screw. Seems to have improved the situation...The loud backfiring has stopped and it doesn’t die on idle anymore. However it’s still a little uneven on idle - the Rev needle bounces about a little. Guess it needs a bit more fine tuning.

On a side note...after doing the above, went for a test ride. Thought it wasn’t as smooth at high revs and making noises so gave it some wallop (not that much). Get to a roundabout, guess who pulls up next to me? The old bill, asking to pullover. Got done for doing 88 in a 50. So at least 3 more points to be expected. Got the other 3 about 2/3 months earlier 🤦🏼*♂️one expensive test ride


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