Carb woes!

[PaulD]

Well I’ve got to admit I’m totally stumped? As per my other posts I’ve stripped and ultrasonic cleaned all four carbs and put them back together and on the bike, unfortunately I’ve made the bloody thing worse in desperation I’ve resorted to trial & error with the air screws and instead of the recommended 3 1/2 turns out I set them at 2 1/2 turns & that made it really bad, looking at the plugs they where black sooty so I’ve put them back to standard. No3 cylinder (counting left to right as you sit on the bike) appears to be burning oil and when trying to balance the carbs I’m struggling to get a matching reading on the gauges on that cylinder. So it would appear I’ve bought a pig in a poke. As I’m used to two strokes I’m really struggling here. Is there anyone in the N/W who knows the carbs on these bikes that might be able to help me out.
Yours in desperation, PaulD

[fossie]

Hi there Paul , the first thing we need to do is remove all the jets, to check the sizes and the clip on the needle is in the correct slot.
As the bike was an Italian, ( who are not know for a rigorous maintainance regimes .....but polishing to make it look good they can excel at!) it may well have have a 4-1 exhaust fitted at some point with k&n type filters. To get it to run with that set up it would need rejetting....... Fast forward to now....to sell at a good price, original exhausts get better prices. But would need original settings to make it run.
Just to confuse the issue if a much later set of zorsts are fitted as from 1997 to 2000 model they would be restricted for jap market and make the bike lean at one point in the range , but if fitted to a bike with 80's carbs upsets the jetting.
So to sum up don't loose heart, it can't be all that bad as it runs .......so back to basics is rhe answer.

[PaulD]

Ok thanks again for the replies, first things first all the jets and needle etc are as the book says. I took the bike for a short steady run of about 5 mile with the air jets set at 2 1/2 turns and when it warmed up it didn’t want to pick up from idle but worse than that it was smoking as I pulled away? When I tried to balance the carbs no3 wouldn’t sync with no4 and no3 plug was very oily hence my diagnosis of a broken ring? I’m going to pull the carbs off again as I’m convinced the float hights are wrong (still starts from cold without choke) where do I measure the float hights on the float? Re the broken ring? Can I get the barrels off with the motor in situ?
Thanks again, Paul

[johnr]

when you rebuilt the carbs, did you replace the o rings and float needles? they go brittle and shrink with age, or if left standing. then they leak fuel through and bollox up the carburation. have you done a compression test? if that cylinder is flooding then the plug will look oily.
when you stripped the carbs, did you remove all the jets?

[PaulD]

Ok first questions first, yes I have a Haynes manual but not the factory one on CD. According to the P.O. he rebuilt the top end and looking at the freshly vacua blasted barrels, head and cases he has but obviously didn’t do a very good job? As to the carbs I did remove and clean every jet, I didn’t replace the needle valves but I did a leak test and they are ok. Re the compression test I can’t do one as my gauge came back from a friend who borrowed it but forgot to mention he broke it! The plug wasn’t just wet it was oily, I’m used to oiled up plugs with racing two strokes lol.

[Uncle Bob]

I would get a new compression tester and do that before going to all the trouble of a top end strip down. Also I would wait for the Litetek vition carb kit and get that installed as well. Both those should be fairly quick to do now you have the experience!

Any experience with TZR250's or Yamaha powervalve's? I have a dead one of those in the garage awaiting strip down...

UB

[PaulD]

Any experience with TZR250's or Yamaha powervalve's? I have a dead one of those in the garage awaiting strip down...

UB

Not powervalves & TZR’s as such but plenty of TZ & RD Yams,when you say dead, how dead are we talking about? Mechanical or electrical?

[PaulD]

Yes you did send the tool plate Mick, thanks. That’s another sherbert I owe you lol

[fossie]

It is very possible that in the past , while the carbs were bunged up from standing that someone "cleaned " out the jets with a needle etc.... This has the undesired of enlarging the jets while the numbers reading like they are standard.
I only say this because it wouldn't be first time someone has spent ages assuming and fannying about. New jets aren't that much from NRP or similar.

[johnr]

i can drop your carbs back at yours now youre back fossie.