Westie1 29 #1 Posted January 18, 2019 Morning all, Just been turning the engine over by hand and I have valve lift on what i think is the compression stroke. Would adjusting the valves stop this or is it designed this way. Thanks Found out it's compression release for anyone wondering the same. Share this post Link to post Share on other sites
Wristpin 400 #2 Posted January 18, 2019 Quite normal. Some manufacturers do it with a centrifugally retracted pin altering the cam profile while others do it with the cam profile itself. Some do it on the inlet, some on the exhaust and one at least, on both. Share this post Link to post Share on other sites
Westie1 29 #3 Posted January 18, 2019 Never heard of it before and I thought how the hell does the cam change if it does lol, amazing really. Got the head back on now and hopefully when I've got it rewired it will run bob on. Share this post Link to post Share on other sites
Fix'em all 49 #4 Posted January 19, 2019 You will also find that older Briggs & also Tecumseh engines around 5hp open the exhaust valve slightly on compression. As the engines wear this can cause starting issues due to low compression. On OHV engines I have countered this by increasing the gap on the exhaust valve & on side valve engines I have removed the exhaust valve & ground a bit off the valve stem (not too much). I am sure Wristpin will not necessarily approve of this practice but it has worked for me on several occasions. 1 Westie1 reacted to this Share this post Link to post Share on other sites
Westie1 29 #5 Posted January 19, 2019 Great info thanks, it was a bugger to start before but I'm hoping that was because I could have thrown a brick between the head and cylinder lol. Share this post Link to post Share on other sites
Wristpin 400 #6 Posted January 19, 2019 8 hours ago, Fix'em all said: You will also find that older Briggs & also Tecumseh engines around 5hp open the exhaust valve slightly on compression. As the engines wear this can cause starting issues due to low compression. On OHV engines I have countered this by increasing the gap on the exhaust valve & on side valve engines I have removed the exhaust valve & ground a bit off the valve stem (not too much). I am sure Wristpin will not necessarily approve of this practice but it has worked for me on several occasions. Hmm !!! Approval or not , increasing the gap by any means is counterproductive as far as compression release for easier starting is concerned. The bigger the gap, the less effective, whatever the release method. That said, a really knackered ( technical term) engine may benefit from all the compression that can be found. AKA an elegant, albeit unorthodox, engineering solution! 1 Fix'em all reacted to this Share this post Link to post Share on other sites
