Suzuki GR650 new carbs

[danieloneill]

Hi All,
im new to the site so hope I have put this in the right area.
I am restoring a 1983 gr650, It had been sitting behind my neighbours shed for 7 yeas. it had been running up to the day he parked it up.
The carbs were left with fuel in them and got all gunked up! when I went to strip the carbs the head off one of the jets broke, long story short after drilling out the jet and trying easy out the rest I managed to crack the housing (rookie!)
ive searched high and low for carbs but no luck, $500 NZD out of mikuni in aus is more than I was willing to pay,
I bought some Chinese 34mm keihin carbs for it with multiple different size jets. when I went ot fire the bike up I couldn't get it to even fire, it eventually let off a big backfire. I let it sit for a bit then tried again. same result!
the gr originally had mikuni cvs but a after doing a bit of google research I decided some mechanical carbs would be easier to tune etc.
I guess what im asking is has anyone every tried something simuliar before?
would the back firing be far too much fuel getting in or to little and it building up then going bang?
once I get it running I should be fine to tune it but just need to get it in the ball park to begin with,
Any help would be greatly apprtreciated.
THanks

[Grumph]

Your problems may be deeper than just the carbs. It uses a TCI ignition - basically a transistorised battery powered system. The ignitor boxes in these systems are known to die from inactivity. Transistors latch and won't move, resistors absorb damp...The random bang is often what you finish up with.
Pull the plugs and turn it over to see if you actually have spark.
It's also possible you have a stuck valve. Again inactivity with a valve open and it can seize in the guide. Usually in 180deg twins it's the left hand exhaust valve for some reason. Check you have compression on both cylinders.

The GR is a rarity in NZ. Ignition wise, GS450 or GSX400 would probably interchange.

[danieloneill]

Thanks grumph
Could you please explain a bit more about the igniter box? I have managed to buy another complete bike, I swapped the carbs over and have the same issue, What exactly doe the ignition box look like, I could swap it over and hopefully that works,
I have had it running for a few seconds on easy start spray before I pulled the bike to bits and repainted it about 10 months ago, the crank gear also came loose and Was spinning on the shaft, it’s on a taper with no key, would that affect the timing?from wat I could tell i don’t think it would,
I checked the timing from some info I found on the net and the piston was at the top (right piston) when the timing marks lined up,
Thanks for your help I look forward to your reply

[Grumph]

The ignitor is literally a small black box. About 70mm X 90 mm with a multi pin plug going into it.
Usually some where close to the battery box on early Suzukis.
Pull the spark plugs and spin the engine over to check for a spark at both plugs before you do anything else.

[danieloneill]

Oh I see, yes I’ve got spark at both plugs. If I have spark will that mean the igniters ok?.

[Grumph]

Oh I see, yes I’ve got spark at both plugs. If I have spark will that mean the igniters ok?.

Good enough to get it running hopefully.

Get a can of engine start spray. I'm hoping you've got at least some sort of air filters fitted - spray the starter fluid up the carb throats, put the filters back on and give it a try.

[danieloneill]

Yes I have tried all that with no joy, I got new plugs in it with plenty of spark.
Because I have removed all the wiring and put back together once painted is there something electrical I may have missed? I’m a bit confused as I’ve got fuel spark and compression.
Very frustrating. I have another motor that I’ll paint up and put in but was trying to avoid that as the one in it looks really good. If a valve was stuck would it still start on one cylinder? Or at least sound like it’s trying to fire?

[pete376403]

Yes I have tried all that with no joy, I got new plugs in it with plenty of spark.
Because I have removed all the wiring and put back together once painted is there something electrical I may have missed? I’m a bit confused as I’ve got fuel spark and compression.
Very frustrating. I have another motor that I’ll paint up and put in but was trying to avoid that as the one in it looks really good. If a valve was stuck would it still start on one cylinder? Or at least sound like it’s trying to fire?
fuel + compression + spark - but is it sparking at the right time? Do the plugs get wet with fuel? If they stay dry that would indicate fuels is not being mixed with the air.

[sidecar bob]

fuel + compression + spark - but is it sparking at the right time? Do the plugs get wet with fuel? If they stay dry that would indicate fuels is not being mixed with the air.

F.A.C.T.S. fuel, air, compression, timing, spark. First year apprentice shit.

[danieloneill]

So I made an apprentice mistake! Turns out I had the coil plugs around the wrong way so although I was getting spark it was at the wrong time, should have realised earlier, I have learnt a lot building this bike (my first bike)
Thanks all for your help!

[merv]

So I made an apprentice mistake! Turns out I had the coil plugs around the wrong way so although I was getting spark it was at the wrong time, should have realised earlier, I have learnt a lot building this bike (my first bike)
Thanks all for your help!

So is it going now?

[sidecar bob]

So I made an apprentice mistake! Turns out I had the coil plugs around the wrong way so although I was getting spark it was at the wrong time, should have realised earlier, I have learnt a lot building this bike (my first bike)
Thanks all for your help!

I started a post about to ask if the plug wires were around the right way, & then I thought about it & decided it probably had a single, twin lead coil with wasted spark & it wouldn't matter. I was wrong.

[merv]

My brother bought this 1983 GR650 at about the end of 1991 and got good service out of it and he kept it in very original condition. He'd added a Givi screen and a backrest behind the back seat and that was about it.

I sold it in Wellington area in 2010 after his death to cancer and trust it is still somewhere giving good service. The pic is one I took in 2010 at the time I was selling it.

They were a rare model. When my bro' bought his one the Suzuki dealers in his town told him no-one was interested in them because they wouldn't pull the skin off a rice pudding.

[pete376403]

Is that the model that had an extra flywheel mass that was used at low revs but was disengaged at higher engine speed?

[merv]

Is that the model that had an extra flywheel mass that was used at low revs but was disengaged at higher engine speed?

That's the one Pete. Can't say you could feel it in any way riding it.

[danieloneill]

Hi guys, sorry about not replying the last few weeks,
Yes the bike is going I’ve had it out for a few rides in the sun.
It’s running pretty good, the only issue I have is that it back fires a bit thru the carb wen I take hand off accelerator and sometimes when just cruising along taking it pretty easy,
When I give it a handful it goes great.
I have put new exhausts on it and pod filters.
Before I start playing with the carbs I thought I’d ask a few questions from you helpful lot.
From what I have read it’s possibly the air mixture screw needs adjusting?that is the screw in the air intake side of the carbs? Do I take pods off while it’s rrunning and adjust them slight and keep taking it for a spin till I get it right? Do both at same time? Really don’t want to screw this one up!
Any help will be greatly appreciated
Thanks

[pete376403]

Do you still have the original airbox? Pod filters can be difficult to jet for.

[danieloneill]

no unfortunalty I don't!