Hi Timothy:
It can be frustrating to troubleshoot problems with the ST 1100 clutch, because there are a lot of different things that can cause problems, the "problems" don't always manifest with exactly the same presentation, and sometimes "the fix" isn't immediately apparent. This is one of the rare instances where you almost have to 'shotgun' the repair process - by that I mean you just throw everything you can think of at the problem, in hope that something will fix it, rather than going through a rational 'paths of influence' analysis before solving the problem with a single 'silver bullet' fix.
Fellow forum members have made some good suggestions above. There's not a lot I can add to what they have suggested, other than to perhaps sort the suggestions into an "order of difficulty" so you can start by doing the easiest / least expensive troubleshooting actions first, then progress to the most difficult / most expensive actions if the first actions didn't solve the problem.
1) Examine the small round brass bush that is embedded in the inboard end of the clutch lever, and examine the rod that goes between the bush and the inside of the clutch master cylinder. The bush tends to wear out over time - the hole in the side of it is only about 50% of the depth of the bush diameter when new, but over time it can wear all the way through. This reduces the amount of movement transmitted to the clutch master cylinder. The bush is cheap. Chances are while you are in there you will find the rubber boot that the rod passes through which fits inside the opening on the side of the master cylinder has perished and needs to be replaced. It's cheap as well. Total time needed for investigation & rectification - less than half an hour. See this post for more detail:
Rebuilt master cylinder & now no forward motion?
2) Find out exactly what engine oil was used last time you had the engine oil changed. The newer engine oils made for cars that are labelled "energy-conserving" are toxic to motorcycle clutches and cause the clutch to slip. You need to use an engine oil that is specifically made for motorcycles and does not have the 'energy-conserving' identification mark on the container. See this post for more information, including an illustration of the 'energy-conserving' label:
T6 10w30
3) Remove the cap from the clutch reservoir and check the clutch fluid level. Sounds fundamental, but it's quick & easy to do. The fluid should be clear, not amber. Because the fluid absorbs moisture over time, it needs to be replaced every two years. It's not that difficult to replace the fluid yourself, but if you have never done it before, try to get together with a fellow ST owner who has done it before who can show you the "tricks of the trade". The fluid is cheap. Here's a link to a discussion about bleeding the clutch to solve a similar problem:
Difficulty shifting down See also this discussion:
Clutch reservoir part
4) It's possible that the clutch slave cylinder is failing. I'm not exactly sure how that would tie in with the 'heat-related' problem you have (clutch not engaging when the bike is hot) - but I do recall when I had my 'clutch wouldn't fully
disengage' problem, I only had the problem when the bike was fully warmed up, not when it was cold. It is a nuisance to replace that slave cylinder and some of the parts are expensive. Plan on more or less a full day of work if you are doing it yourself. Here's a how-to:
ST1100 - Replacing the Clutch Slave Cylinder
5) I'll put investigation and rebuilding of the clutch master cylinder way down towards the bottom of the list, this because it should not be affected by heat in any way. There is a kit available from Honda to rebuild the master cylinder. I did this on my bike, and it didn't make any difference.
6) Examine the clutch hose. It might be swelling a bit, likely down by the engine end of it, because it is getting old and perishing. Honda no longer sells clutch hoses, you will need to go to a third party - perhaps Galfer - to get a new one.
Good luck with it all, keep us informed, and don't hesitate to post questions here if you encounter any difficulty.
Michael
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www.partzilla.com
