Hi, I'm working on a neighbor's 1994 ST1100 that he had disassembled way back in 2014 because of some coolant leaks from a couple hoses and I basically got the bike still all disassembled so... even though I'm an excellent mechanic (double Master ASE certified and also have been working on motorcycles for 40+ years) it's obviously a challenge to try to figure out how everything goes back together since I didn't take it apart. He fortunately provided me with three service manuals including even the genuine Honda service manual, BUT, some of the systems on this engine aren't thoroughly explained in the manuals. I replaced all the coolant hoses with genuine Honda ones and also many other parts that were bad due to it having sat for over 10 years with the original gas in it (had to find a good used fuel tank and pump assembly due to the tank being so bad inside with varnish and also rust from condensation above the fuel level) and I cleaned and rebuilt the carbs BUT I didn't pull off the CV covers to inspect the diaphragms because I decided it probably would be safer to not disturb them at all due to their age.... granted now in hindsight I should have disassembled and inspected and cleaned them too. Anyways, I fired it up for the first time last night (also new carb to intake boots) and it took a little bit to get it fired up but it actually ran pretty good after a minute or two. My issue is that the idle seems lean and is a little high and I noticed that both of the two big hoses that go to the secondary filter assembly in front are flowing a LOT of air (vacuum) into the carbs. After doing a few hours of research online and especially through this forum, I have come to the conclusion that there's probable a couple torn or leaking slide valve diaphragms? I'm thinking that the vacuum that's generated to lift the slides is getting through some (or all?) the diaphragms and that's causing the lean condition? When I plug off both of those hoses it idles excellent and takes throttle relatively well but I'm sure that none of the slides aren't opening or very little. The bike is still quite a bit apart so I haven't actually tried riding it but I know that's not even really needed at this point since I can tell there's a carb related issue. My question is, am I right in thinking that if it has a leaking diaphragm(s?) that I will see excessive vacuum flowing through the secondary filter hoses? I'm going to pull the carbs back off again this afternoon and pull the carbs all apart again and this time I'll pull apart the CV slides and diaphragms too. At this point I'm about 90% convinced I'll probably see it needs new diaphragms unfortunately... ($$) but I thought I'd post this on here to see what you all think regarding the vacuum flow through the secondary filter hoses.
Also, on a side note, I noticed that the cooling fan never kicked on and I bypassed the cooling fan temp switch and it turned on and runs perfectly... so it also needs a new cooling fan temp switch. Does anyone know of any "cross reference" type of temp switch I might be able to use rather than spending the $80+ that Partzilla etc. want for the genuine Honda one? I'm sure it's a pretty generic type of switch (probably only like $14) that might not be hard to match up something locally and Oreiley's or Napa or whatever but I figured I'd ask on here since maybe someone has a cheaper alternative I can get to help save him some money since the genuine Honda CV diaphragms are definitely not cheap! Maybe someone on here knows where I can get new diaphragms cheaper than like $124 each through Partszilla ect?
Also, on a side note, I noticed that the cooling fan never kicked on and I bypassed the cooling fan temp switch and it turned on and runs perfectly... so it also needs a new cooling fan temp switch. Does anyone know of any "cross reference" type of temp switch I might be able to use rather than spending the $80+ that Partzilla etc. want for the genuine Honda one? I'm sure it's a pretty generic type of switch (probably only like $14) that might not be hard to match up something locally and Oreiley's or Napa or whatever but I figured I'd ask on here since maybe someone has a cheaper alternative I can get to help save him some money since the genuine Honda CV diaphragms are definitely not cheap! Maybe someone on here knows where I can get new diaphragms cheaper than like $124 each through Partszilla ect?
