Steelfitter Posted July 16, 2009 Share Posted July 16, 2009 I just got a master cyl rebuild kit today from Old Bike Barn for my son's friends xs400. I've rebuilt automotive master cyl before but this will be my first motorcycle master cyl. Any tips I should be aware of or is it pretty much straight forward? Link to comment Share on other sites More sharing options...
Steelfitter Posted July 18, 2009 Author Share Posted July 18, 2009 I got it all cleaned up and installed a new piston and seals in the master cyl and the front brakes actually work now. The bike had sat for 7 years before my sons friend bought it and asked me to resurrect it which took some serious carb cleaning to do and it does idle well but seems to surge when under a load. Carbs still need synced but there is at least 1 lifter that has way too much lash, it ticks pretty bad and gets worse as it's warmed up after a short ride and that needs to be dealt with first before the carbs can be dialed in correctly. Problem is that I found out that setting valve lash on the xs400 is a bit more involved than it is on my Honda cb350 and the Yamaha needs a special tool and lifter caps to get it done. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted July 18, 2009 Moderator Share Posted July 18, 2009 I got it all cleaned up and installed a new piston and seals in the master cyl and the front brakes actually work now. The bike had sat for 7 years before my sons friend bought it and asked me to resurrect it which took some serious carb cleaning to do and it does idle well but seems to surge when under a load. Carbs still need synced but there is at least 1 lifter that has way too much lash, it ticks pretty bad and gets worse as it's warmed up after a short ride and that needs to be dealt with first before the carbs can be dialed in correctly. Problem is that I found out that setting valve lash on the xs400 is a bit more involved than it is on my Honda cb350 and the Yamaha needs a special tool and lifter caps to get it done. Aye, I think you will need different thickness shims too if its the dohc model. take your gaps first and see what you need. Link to comment Share on other sites More sharing options...
dtmf Posted July 20, 2009 Share Posted July 20, 2009 I got it all cleaned up and installed a new piston and seals in the master cyl and the front brakes actually work now. The bike had sat for 7 years before my sons friend bought it and asked me to resurrect it which took some serious carb cleaning to do and it does idle well but seems to surge when under a load. Carbs still need synced but there is at least 1 lifter that has way too much lash, it ticks pretty bad and gets worse as it's warmed up after a short ride and that needs to be dealt with first before the carbs can be dialed in correctly. Problem is that I found out that setting valve lash on the xs400 is a bit more involved than it is on my Honda cb350 and the Yamaha needs a special tool and lifter caps to get it done. here's a like i found for the tool http://www.z1enterprises.com/detail.aspx?ID=1698 . it;s for the xs650 but it look's just like the one for the xs400 dohc . for 12 buck's it's worth a try . i also plan on replacing the vavle shim's on my 82 xs400 seca . once you have the right shim's it look's like a very easy job to do . here's a link to the valve shim's they are down in the engine section http://shop.wemoto.com/index.dyn?oid=2147871 Link to comment Share on other sites More sharing options...
Moderator drewpy Posted July 20, 2009 Moderator Share Posted July 20, 2009 here's a like i found for the tool http://www.z1enterprises.com/detail.aspx?ID=1698 . it;s for the xs650 but it look's just like the one for the xs400 dohc . for 12 buck's it's worth a try . i also plan on replacing the vavle shim's on my 82 xs400 seca . once you have the right shim's it look's like a very easy job to do . here's a link to the valve shim's they are down in the engine section http://shop.wemoto.com/index.dyn?oid=2147871 xs650 don't have shims, i think you mean xs750, 850 and 1100 Link to comment Share on other sites More sharing options...
Steelfitter Posted July 25, 2009 Author Share Posted July 25, 2009 From the moment I first got the bike running it idled well but had hardly any power when accelerating and was lucky to be able to do 60mph. I had replaced the fuel valve seats along with new bowl gaskets and noticed a slight difference between the new gaskets compared to the old ones. I didn't think much of it and used the new gaskets as they were but I was still confounded as to why it seemed to be starving for fuel when under a load so the carbs came off again. In my "process of elimination" I installed the original bowl gaskets, cleaned out the main jets with a torch cleaning tool which opened up the main jets just a tad and sprayed all the passages clear again with carb cleaner and compressed air. The end result is that the bike now runs fantastic and pulls well when under a load. Was the "fix" a result of opening the main jets up a bit? Was it using the correct float bowl gasket? Was it a result of cleaning the carbs again or a result of all the above? I can't say but I'm just pleased that it's starting to run like it should and considering that the valve lash still needs to be adjusted and the carbs properly synced tells me the bike has even more to offer. Link to comment Share on other sites More sharing options...
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