Finally got my CB750K4 out on the road wednesday. I have a few problems Im running into and could use some advice on.
1. Starting between 35-40mph and ending around 50mph when at a steady cruise the front end starts to bounce like you're riding down a washboard. It was very pronounced the first day I rode it and I had noticed some fork oil seepage around the seals. Yesterday night I changed out the fork oil. It had ATF in there from the previous owner, I flushed the forks out with some 5w30 and then refilled them with 150cc of 15wt fork oil. I checked the axle retaining nuts on the bottom of the fork legs and got about another 1/2 turn out of each one. Finally the bike has a dual disk conversion and I think the brake drag was too high so I loosened the adjusters until the wheel spun freely without the brakes on. After this work I rode the bike again and it definitely seemed better but the bounce is still there although more intermittent and not as pronounced as before. It was so bad before the work I didn't take the bike over 50 but last night I got up to about 70 and it was smooth at that speed. I have not checked the balance on the front wheel yet but there are weights on it. My next step was going to be trying some of that PJ1 tire balancing stuff. To me it feels like the bounce is in the forks but I'm open to suggestions. I was reading on here in the fork FAQ and the fork fill is 135-140cc with a drain and 155-160cc dry. I read the service manual and it didnt specify just a drain refill level so I split the difference and went with 150cc. The forks were open to drain for about an hour and I cycled them up and down a few times to get everything out. Think I should put another 10cc in there?
2. The bike has a very pronounced rattle in the engine when running. With the bike in neutral and the clutch out its very loud, when you engage the clutch it gets a little better but there is still quite a rattle. I looked around and found the cam chain adjustment procedure and did that. Removed the points cover, put the timing mark in-line with the left side of the spring post by the 1/4 mark, loosened the jam nut and backed the bolt out till it touched the starter cover and the re-tightened it. After the first time of doing that the bike seemed to run much smoother and accelerate better but the noise was still there, maybe a little quieter then before but very noticeable still. I did the procedure again only this time with the bolt backed out I tapped on the tensioner housing with the plastic end of a screw driver to loosen it up if it was sticking. Still the same results afterwards. I read that you can get a rattle noise in the engine if the carbs arent synced and after changing the spark plugs I suspect they may need some adjustment as the 2 & 3 plugs were a bit darker then 1 and 4 but this sounds like a pretty pronounced mechanical rattle to me. Just FYI I installed new NGK plugs when I adjusted the cam chain the first time Wednesday and I change the oil with Castrol 10w40 motorcycle oil before the engine was started for the first time.
3. The clutch wasn't engaging until the very end of the lever travel so I did a complete clutch adjustment per the manual. Loosened the cable, removed the side cover, loosened the jam nut, turned the screw until resistance and then back 1/4 turn and then adjusted the cable per spec. The clutch now engages where it should in the lever travel but I'm getting slippage especially on the 1-2 shift when getting on it. Pretty sure this means it will need a clutch job but I wanted to check if there is anything else I can adjust first. After riding it a bit more today I have to be very slow and deliberate on the 1-2 shift to get it into gear otherwise it goes into neutral.
4. Just last night while riding the neutral indicator light started coming on while riding in gear. It comes and goes when shifting but its on more often then not now. Possible ground issue or something else? What should I check?
That's about it for now, thanks for any assistance.
1. Starting between 35-40mph and ending around 50mph when at a steady cruise the front end starts to bounce like you're riding down a washboard. It was very pronounced the first day I rode it and I had noticed some fork oil seepage around the seals. Yesterday night I changed out the fork oil. It had ATF in there from the previous owner, I flushed the forks out with some 5w30 and then refilled them with 150cc of 15wt fork oil. I checked the axle retaining nuts on the bottom of the fork legs and got about another 1/2 turn out of each one. Finally the bike has a dual disk conversion and I think the brake drag was too high so I loosened the adjusters until the wheel spun freely without the brakes on. After this work I rode the bike again and it definitely seemed better but the bounce is still there although more intermittent and not as pronounced as before. It was so bad before the work I didn't take the bike over 50 but last night I got up to about 70 and it was smooth at that speed. I have not checked the balance on the front wheel yet but there are weights on it. My next step was going to be trying some of that PJ1 tire balancing stuff. To me it feels like the bounce is in the forks but I'm open to suggestions. I was reading on here in the fork FAQ and the fork fill is 135-140cc with a drain and 155-160cc dry. I read the service manual and it didnt specify just a drain refill level so I split the difference and went with 150cc. The forks were open to drain for about an hour and I cycled them up and down a few times to get everything out. Think I should put another 10cc in there?
2. The bike has a very pronounced rattle in the engine when running. With the bike in neutral and the clutch out its very loud, when you engage the clutch it gets a little better but there is still quite a rattle. I looked around and found the cam chain adjustment procedure and did that. Removed the points cover, put the timing mark in-line with the left side of the spring post by the 1/4 mark, loosened the jam nut and backed the bolt out till it touched the starter cover and the re-tightened it. After the first time of doing that the bike seemed to run much smoother and accelerate better but the noise was still there, maybe a little quieter then before but very noticeable still. I did the procedure again only this time with the bolt backed out I tapped on the tensioner housing with the plastic end of a screw driver to loosen it up if it was sticking. Still the same results afterwards. I read that you can get a rattle noise in the engine if the carbs arent synced and after changing the spark plugs I suspect they may need some adjustment as the 2 & 3 plugs were a bit darker then 1 and 4 but this sounds like a pretty pronounced mechanical rattle to me. Just FYI I installed new NGK plugs when I adjusted the cam chain the first time Wednesday and I change the oil with Castrol 10w40 motorcycle oil before the engine was started for the first time.
3. The clutch wasn't engaging until the very end of the lever travel so I did a complete clutch adjustment per the manual. Loosened the cable, removed the side cover, loosened the jam nut, turned the screw until resistance and then back 1/4 turn and then adjusted the cable per spec. The clutch now engages where it should in the lever travel but I'm getting slippage especially on the 1-2 shift when getting on it. Pretty sure this means it will need a clutch job but I wanted to check if there is anything else I can adjust first. After riding it a bit more today I have to be very slow and deliberate on the 1-2 shift to get it into gear otherwise it goes into neutral.
4. Just last night while riding the neutral indicator light started coming on while riding in gear. It comes and goes when shifting but its on more often then not now. Possible ground issue or something else? What should I check?
That's about it for now, thanks for any assistance.
