Valve backlash issue...or maybe not?

Training_Wheels · 06-19-2023, 01:44 PM

I am new to the Hawk and China Riders. I have a question that I hope someone can answer.

This weekend I decided to check the valve backlash after about 300 miles of riding. I while doing this I noticed that at TDC on the compression stroke the exhaust valve backlash was over 1mm and TDC on the exhaust stroke the clearance was close to .05mm. After considering this I thought the clearance on the exhaust valve must have been set by the factory in the wrong way, at TDC on the exhaust stroke. I knew that changing this by resetting the backlash on the compression stroke at TDC would have an effect on the exhaust valve on the exhaust stroke and is does keep the valve open for part of the intake portion of the stroke, as in a scavenging type of activity. So, has anyone every seen this? The engine starts fine and I ran it a short while with now discernable issues but still hope someone else can confirm my thesis. Thanks!

Emerikol · 06-19-2023, 02:45 PM

Kind of confused reading your post, but I'll give it a shot. Valve lash can be checked with the rockers anywhere on the cam except on the cam lobe itself. Generally, lash should be checked at TDC on the compression stroke because both rockers will be on the round part of the cam, and not the lobe. It just makes it easier from a maintenance perspective. The valves were probably way out of spec from the factory, and in your case they were out of spec in the way that did you the most good. Most of us have bikes that came from the factor with absolutely zero play. In any event, if you've made the adjustment (and remembered to check it twice) and everything is running well, you'll probably be just fine. Remember, tappy valves are happy valves. You should be able to hear a little valvetrain noise when the engine is running. I run my valves at 0.04" on the intake side and 0.06" on the exhaust side. Since the intake valve constantly has the cooler fuel/air charge, it can be a bit tighter. Please note that's in INCHES, not MM. 0.05mm is just a touch under 0.02". That's way too tight for these engines. Hope this helps you out some!

Training_Wheels · 06-19-2023, 04:30 PM

Emerikol,

Thanks for the reply!
I was really confused, concerned that the setting was so loose from the factory. I thought, "Surely they could not have missed this so badly".
I set the valves at a loose .05MM based on the manual that came with the bike. It seemed a little close to me but ....I am glad I asked the more seasoned on this!

I prefer the "tappy happy" sound as well! Thanks for the advice. I will open them up!

Emerikol · 06-19-2023, 05:20 PM

I can promise you they didn't use feeler gauges to check the lash when they were putting the engine together. It was probably some guy doing it by feel wherever the valvetrain was, not even concerned with TDC. In the end, it worked out for you and it looks like you dodged a bullet. There are more than enough stories of people burning up valves in no time at all because they put gas in the bike and just took off. Hope you get a lot of enjoyment out of your new Hawk!

06-19-2023, 01:44 PM	#1
Training_Wheels Join Date: Jun 2023 Posts: 3	Valve backlash issue...or maybe not? I am new to the Hawk and China Riders. I have a question that I hope someone can answer. This weekend I decided to check the valve backlash after about 300 miles of riding. I while doing this I noticed that at TDC on the compression stroke the exhaust valve backlash was over 1mm and TDC on the exhaust stroke the clearance was close to .05mm. After considering this I thought the clearance on the exhaust valve must have been set by the factory in the wrong way, at TDC on the exhaust stroke. I knew that changing this by resetting the backlash on the compression stroke at TDC would have an effect on the exhaust valve on the exhaust stroke and is does keep the valve open for part of the intake portion of the stroke, as in a scavenging type of activity. So, has anyone every seen this? The engine starts fine and I ran it a short while with now discernable issues but still hope someone else can confirm my thesis. Thanks!
	1

06-19-2023, 02:45 PM	#2
Emerikol Join Date: Oct 2016 Location: Carrollton, GA Posts: 1,465	Kind of confused reading your post, but I'll give it a shot. Valve lash can be checked with the rockers anywhere on the cam except on the cam lobe itself. Generally, lash should be checked at TDC on the compression stroke because both rockers will be on the round part of the cam, and not the lobe. It just makes it easier from a maintenance perspective. The valves were probably way out of spec from the factory, and in your case they were out of spec in the way that did you the most good. Most of us have bikes that came from the factor with absolutely zero play. In any event, if you've made the adjustment (and remembered to check it twice) and everything is running well, you'll probably be just fine. Remember, tappy valves are happy valves. You should be able to hear a little valvetrain noise when the engine is running. I run my valves at 0.04" on the intake side and 0.06" on the exhaust side. Since the intake valve constantly has the cooler fuel/air charge, it can be a bit tighter. Please note that's in INCHES, not MM. 0.05mm is just a touch under 0.02". That's way too tight for these engines. Hope this helps you out some! __________________ First Rule of Aviation: -Never Pass Up The Opportunity to Pee I was struggling to get my wife's attention; I sat down on the couch and looked comfortable. That did the trick! My wife says I only have two faults. I don't listen and something else... If at first you don't succeed, try doing it the way I told you to... The Stable: 2005 Yamaha V-Star 650 - SOLD 2015 Suzuki DR 650 2015 RPS Hawk 250 - SOLD 2016 Ural Gear Up
	2

06-19-2023, 05:20 PM	#4
Emerikol Join Date: Oct 2016 Location: Carrollton, GA Posts: 1,465	I can promise you they didn't use feeler gauges to check the lash when they were putting the engine together. It was probably some guy doing it by feel wherever the valvetrain was, not even concerned with TDC. In the end, it worked out for you and it looks like you dodged a bullet. There are more than enough stories of people burning up valves in no time at all because they put gas in the bike and just took off. Hope you get a lot of enjoyment out of your new Hawk! __________________ First Rule of Aviation: -Never Pass Up The Opportunity to Pee I was struggling to get my wife's attention; I sat down on the couch and looked comfortable. That did the trick! My wife says I only have two faults. I don't listen and something else... If at first you don't succeed, try doing it the way I told you to... The Stable: 2005 Yamaha V-Star 650 - SOLD 2015 Suzuki DR 650 2015 RPS Hawk 250 - SOLD 2016 Ural Gear Up
	0

06-19-2023, 04:30 PM	#3
Training_Wheels Join Date: Jun 2023 Posts: 3	Emerikol, Thanks for the reply! I was really confused, concerned that the setting was so loose from the factory. I thought, "Surely they could not have missed this so badly". I set the valves at a loose .05MM based on the manual that came with the bike. It seemed a little close to me but ....I am glad I asked the more seasoned on this! I prefer the "tappy happy" sound as well! Thanks for the advice. I will open them up!
	1