GT380 Carb Issue

[dreschr]

I’m having issues with carbs after an engine rebuild, the carbs were sent to a local two stroke workshop for vapour cleaning and rebuild and I also fitted an electronic ignition. When I started the engine it started very easily on middle and right cylinder but the left was cold, checked for a spark on that cylinder and it was very strong. I removed the carbs as one had a leak form the overflow, disappointingly I found that the float was partially full of petrol and the original gasket re-used I therefore replaced all floats purchased from ebay. I removed the air pilot screw and main jet and used compressed air to give them a clean through. Carbs back on the bike and started the engine with no air box, it started good on middle and right and the left also started but was "popping" when I refitted the air box the left again wouldn’t run.
All pilots set at 1 1/2 turns out. The expensive carb rebuild appears to have not included new parts??? so my next plan is to buy a complete set of parts and rebuild please can anyone advise which kit is suitable/proven and what else I should do to get the engine "running" smoothly on all three?? I need help soon or tools will be flying!! very frustrating, so close but not there, the bikE looks ace with its new paint and chrome.
Regards- Rich

[barney01]

Hi Rich.
Firstly vapour blasting the carbs is only effective for the outside look and appearance. The internal passageways, which cannot be seen, can only be cleaned by using an ultrasonic cleaner or carb cleaner blasted out with compressed air. Secondly you say you removed the main jet and the pilot air screw. Did you also remove the pilot jet? Have you checked the fuel level? In particular the left carb. What sort of Electronic ignition is fitted and have you checked the timing?
Is the filter element clean and unobstructed?
One last check. Is the choke piston on the offending carb moving up and down as it should and not stuck closed.
You could try a spray of starting fluid in the back of the carb to get it running.

[willowden]

If you need carb internals , check out Steve at Motocarb. Mikuni specialist.
Engine rebuild , who did it ? Have you checked the compressions / crank seals.
Popping back , has the cylinder head & barrels been torqued correctly ?

[Alan H]

Should have sent them to Baz. He does a great job. Done a few sets for me.

[Gary66]

Pretty certain i bought my carb kit from cruzin image. The kit was fine and the bike runs well. The only issue is on start up after being laid up with fuel turned off the centre cylinder lags behind, whether its the last to get fuel in the float bowl i dont know. I have to rev the bike for a few seconds and then it bursts into life and thats the end of the issue till next cold start time. This may be down to me building up the carbs and possibly not getting something right, not sure, once its up and running it runs spot on so i just put up with it

[BAZ]

Have you balanced the carbs...cheers Barry.

[dreschr]

Hi Folks

Big thanks for the prompt reply’s, spent some time with the "War Office" in the garden centres sorting bedding plants etc. So hence a late reply but now garage time.

OK- Engine rebuild I did myself but crank and carbs sent to the local 2 stroke workshop to sort, crank rebuilt with new seals and bearings. The cylinders looked great so i deglazed but did fit new pistons and rings, the compression feels great by the kick bit I have not taken individual pressure readings using a gauge. Please note I have played about with motorbikes since I was twelve and spent 38 years as an Engineer with BP, defiantly not an expert but have a reasonable understanding but Im so prepared to listen to advice as I've never done a GT before

Electronic ignition was from the wonderful Ewe of Accent, timing ? just followed the instructions i.e. red light goes out when the middle pot is at TDC and then I believe the other cylinders follow. During the rebuild I ensured the dot on the crank gear aligned with the marker arrow and then installed the timing propeller at left cylinder TDC. If the timing was too far out surely the middle and right cylinder would not "run" as smooth as they do? tick over is perfect, I was surprised the left cylinder was cold as the engine sounded great, but that could be my lack of understanding of the sound of a 3 cylinder two stroke??

Carbs- When I changed the floats and removed the main jet I did this in position with carbs pulled to one side as I was desperate to get the bike running, therefore due to lack of access I did not remove the needle jet.
So my plan is to get a complete set of carb parts that include all jets, totally strip the carbs and use carb cleaner with a compressor setting at PSI set as high as I can get an then blow all parts. Ive never balanced carbs before so please advise what this requires. Secondly is it possible to run one cylinder at a time (pull plug leads) and adjust each carb in turn until it "sounds correct" or could this damage the crank?

I’ve not checked the choke operation of the left pot but will do when I remove the carbs. What ive read on the forum suggests I should have sent them to Baz?

Big Thanks Guys for your help to date, Ive attached a couple of photos for your interest.
Rich

[barney01]

Accent ignition is by far the best electronic ignition. Baz is on the forum and is the man to go to sort carbs. The best way to balance carbs is with an airflow meter. Running the engine on just one cylinder wont damage the crank.
Nice looking ride you have there BTW.

[Alan H]

Not sure how you managed to get the propeller to line up on tdc, as it has a locating pin to locate the propeller marks coinciding at aprox 3mm btdc (24 degrees +3/-2).
Look at http://www.alpha-sports.com/suzuki_parts.htm . Pick year, model, contact breaker and you'll see it clearly.
It's easy to check if all cylinders are running - use the wet finger test - quickly! - on the down pipes near the barrel joint - unless you have a laser temp gauge. These are very handy so that you can check if the cylinders are running equally.
Carbs. Baz strips, cleans and 'rumbles' them in beads so they are very clean, then replaces jets with originals unless they are u/s, then replaces with Mikuni, not after market.
Slow running is pilot circuit and jet plus slide cutaway mainly, fast running is main jet, emulsifying tube, needle and slide again. It's a bit more complicated than that, but that's basically it.
You either need to get the carbs off and remove the pilot and air jets, blow them through with carb cleaner and check there's no 'spluttering' or onesidedness with the spray out of the orifices.
Last thursday, I got a set of carbs that had been Baz'd, fitted them to the 550 on Saturday, hit the button and it ran on 3. Tickover was high at 1500 instead of 1000/1100, otherwise perfect. I know carbs reasonably well and have done a couple of triple sets, but he does them better. Choice is yours. Obviously it costs, but I think it's money well spent, and so do the wallet moths.
I have a scanned copy of a service manual that I bought back in 1972. It's still relevant with details for ALL early models, and many details for later models (gearing, charging, tolerances etc.) If you want a copy foc, pm me your email address and I'll pop one in the 'post'.

[BAZ]

This is what i use https://www.ebay.co.uk/itm/Dual-Carbure ... Sw8oFXyhvU works great..