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Post by shiloh on Jun 25, 2014 5:34:35 GMT -5
Hi all, need input on this little bikes performance.
It seems to me to be running on the rich side, maybe too much. Original carbs/jetting, original air system, no leaks, period dencos, timing spot on, cold start plungers adjusted properly, plugs a little if not a lot on the sooty side, equally on all 3.
What is happening is that it burbles through 1st gear almost like its being flooded, not a smooth power curve in the least, a little less into second and better in third and so on. Needles in the middle position, air screws 1-1/2 out, and worst of all fuel consumption is way out to lunch, I know these bikes are hungry, but this thing right now is a glutton!
I`m thinking the pipes are the issue to the tuning problem and I`m not sure which way to proceed. I`ve found conflicting info about tuning and jetting concerning after market pipes, i.e. no jetting required if running factory air box,... you must rejet with aftermarket pipes..... bla bla bla.
So who has tuning experience with s2`s and can I be steered in the right direction.
I should also mention the engine is stock, on 1st over bore, NOS pistons and rings.
All suggestions and help greatly appreciated.
Shiloh aka Perry, Rick, never on time for dinner........
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Post by Walms on Jun 25, 2014 6:05:57 GMT -5
Probably the best advise I can give you is to focus on throttle position at cruise so you can nail down the brass component to replace. I put a pointer on my throttle so at a quick glance you know the throttle opening for reference. The following diagram is for a Keihin carb but the same thing applies "generally" for Mikuni's as well.  |
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Post by mraxl on Jun 25, 2014 6:38:11 GMT -5
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Post by Walms on Jun 25, 2014 6:41:01 GMT -5
This is the way I go about it... Not necessarily "the way" but it's my way...  For the idle circuit, i like to give the throttle a quick wicking and get zero bog to confirm it's not lean. When cruising, get the bike at a happy rpm so you can minimize the throttle opening, then listen for 4 stroking as an indicator that the idle circuit is too rich. Turn out the idle screws if to rich, turn them in if too lean. You should be about 1-1/2 turns out from the stop... If more than 2 turns out, best to go down in the pilot, if less than 1 turn out, best to go up on the pilot. As far as the mid throttle goes, I'll assume you can get it dialled in with needle clip position without changing needles or needle jets... Again, check for bog when wicking it while cruising at half throttle and look for a lean bog or ping, for rich, just listen for it loading up, 4 stroking, snap crackle pop sort of thing. For jetting the main, ideally you start rich, and keep jetting down until it will run clean without drowning out... If the other circuits are dialled in properly first, I find it's easier to dial in the main as it seems the bleed through from the other circuits can sometimes give you a false impression. What I like to do for the main is get the bike just on the pipe at half throttle and let it stabilize there for a minute... This should be a slightly lean condition because normally the needle and pilot are set off the pipe. I then give it beans and listen for deto but most will tell you to do plug chops to know for sure. |
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Post by Deleted on Jun 25, 2014 15:18:38 GMT -5
Remove the air filter and see if it improves. I'd first look at the carbs closely for something screwed up. inside.
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Post by H2 Dude on Jun 25, 2014 18:32:20 GMT -5
On my sons I had to go to 22.5 as Dale noted and put the clip in the 2nd notch from the top.
Mine..the pilot was Ok but again I had to go to the 2nd notch.
Ivan now makes the carb kits and one will going into my S2A
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Post by shiloh on Jun 25, 2014 19:24:14 GMT -5
Thanx guys for the great advise. Some of the things Walms mentioned is telling me I may be a little lean in one of the systems, she hits hard on the pipe at around 6.5k on all gears but first. After re reading the carb tuning link, the first gear issue is prob rear end gearing, new sprocket on the way from Jt Sprockets, after I get that installed I,ll go for rip and see what btm improvements are like and go from there. Again thanx, great having this wealth of knowledge just click away. |
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Post by shiloh on Jun 25, 2014 20:13:26 GMT -5
On my sons I had to go to 22.5 as Dale noted and put the clip in the 2nd notch from the top. Mine..the pilot was Ok but again I had to go to the 2nd notch. Ivan now makes the carb kits and one will going into my S2A Good point I'm thinking changing the needle clip possiton will help. But after I change gearing and dick around with pilot settings. |
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Post by shiloh on Jun 25, 2014 20:16:42 GMT -5
Remove the air filter and see if it improves. I'd first look at the carbs closely for something screwed up. inside. Tryed that no real improvement. |
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Post by Walms on Jun 25, 2014 21:48:55 GMT -5
What happens at 6k in 1st? It should be the most forgiving gear unless it's falling on it's face? Maybe that means the main is so small it limits the rev? I've never had that condition myself.
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Post by shiloh on Jun 26, 2014 4:46:53 GMT -5
What happens at 6k in 1st? It should be the most forgiving gear unless it's falling on it's face? Maybe that means the main is so small it limits the rev? I've never had that condition myself. The only way I could describ it is messy, its not a smooth power curve like the othet gears, burbly and erratic. |
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Post by shiloh on Jun 29, 2014 15:18:12 GMT -5
Ok, so I got the 43t sprocket on the back, needles second from the top, and the air screws at 1-1/4 turns out. Its alittle boggy nailing it out of first but pulls hard all the way to 8.5k. The rest if the gears the same, scary conpaired to before. No more 4 stroking and noticed no detonation/pinging. Another thing I noticed was the oil punp cable was snagged at half open at idle, that could explain some of the problems I was experiancing. Opps  I think its close for now, sounds way cleaner too. |
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Post by Curtis on Jun 29, 2014 18:17:18 GMT -5
A "messy" sound usually means carbs are not synced properly, and that will create havoc
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Post by shiloh on Jun 30, 2014 5:23:35 GMT -5
A "messy" sound usually means carbs are not synced properly, and that will create havoc A syncing I will go......., I figured this should be checked again, but I was all tuckered out from a long hot exhausting wkndi n London. |
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Post by shiloh on Jul 1, 2014 12:22:22 GMT -5
re-sync`d the carbs and checked the timing, a little off so I dialed it in, running even better now. I think I`m happy now, I`ll run her this way for a while and see how it holds up.
Thanx for the input, and have a safe and happy Canada Day.
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