The Royal Enfield Bullet Blog
Wednesday, July 14, 2004
Bullet Compression Loss
A couple of weeks ago my woman needed to drive down to Cuero from Austin. I decided to follow her Toyota Corolla on my Bullet.
I got it out of the garage, put my gear on, and, in the 95 degree heat, kicked it to life.
Well, not quite.
To my horror I discovered that I could kick through all 4 cycles without using the decompression valve. The last time I'd ridden was about three weeks previous. I'd ridden a long way in pretty high temperatures. I didn't *want* to have missed so much riding time, but my family situation had demanded it. We all know how that goes sometimes. I wasn't thinking about how long it had been since I'd ridden though, I was thinking about what damage the long ride in the heat might have done to a valve or the rings.
My woman was anxious.
I kicked and kicked and kicked -- checked the decompression valve to see if it was stuck open -- then kicked some more.
"Look, I need to get going babe ..."
She had that semi-annoyed, quizzical look on her face of somebody who has a schedule to keep and you're the one keeping them from adhering to it.
"I don't understand", I muttered. "It was fine last time I rode it."
Kick. Kick kick kick.
Finally it thumped once or twice and died.
Sweating, I kicked some more, and when that failed put my head down on the forks. I couldn't take my Jeep, because it was misfiring -- and now I couldn't take my Bullet because it wouldn't fire at all.
In frustration I admitted defeat.
"Sorry babe. I just don't know what's wrong. Guess it's not my day to be riding. You'll have to go alone."
Then I kicked once more to punctuate the failure.
A-thump-thump-thump-thump-thump-thump-thump ...
I revved the motor gently, she kept going, my woman rolled her eyes.
"Finally!!!"
Off we went. Of course, we had to turn around and come back to the house after about half a mile because she forgot some paperwork she needed.
I grinned and figured that was my revenge, but on highway 183 she kept creeping way out in front of me. I pulled up next to her at a stoplight in Lockhart.
"Baby," says I, "I told you this bike only does 60 to 65 comfortably. You gotta slow down."
She bit my head off and said she'd never gotten above 55 and most of the time was at 50, and if she went any slower then she'd cause a wreck.
Ahead of us, down south toward Luling, I could see some rather ominous looking black clouds.
I told her I'd see her back at the house, and I figure she was glad to be rid of me.
On the way back I figured out using milage signs that my Bullet was going 60 MPH when the speedo was jumping around the 70 MPH mark. Heh. Optomistic Indian engineers! The other thing I pondered was why the bike hadn't wanted to start.
Thirty minutes later I was in my driveway testing the compression. It was solid -- no problems at all. I could no longer kick through all 4 cycles without actuating the decompression valve.
So, what was the problem?
The Bullet theoreticians over at the Yahoo Group Bulletech came up with what I figured was a reasonable explanation: when you let the Bullet sit for an extended period you can get a case where the oil lining the cylinder wall drains out to such an extent that there's not enough fluid to create a hydrostatic seal between the rings and the cylinder wall.
At first that seemed ... well, unlikely.
But several posts showed up describing the same symptoms I had and describing that getting the bike running again -- however briefly -- could solve the issue. One poster said he had actually taken out the plug and squirted a small amount of oil in the cylinder -- and it fired up first kick after that.
That convinced me: hydrostatic seal it was.
The only thing that still annoyed me was how fast ... er, slooowww ... my Bullet was going. Next move: putting on the 18 tooth sprocket I've got sitting in my parts bin. It may not help a lot, but I think it ought to get me going a little bit faster without the high rev screech and vibrations from hell -- and I've got a sprung seat.
Actually I like going slow. But it will be some time before I get or build a big twin, and so if I can up the speed just a little and do some mechanical work for pleasure it's a win/win situation.
I got it out of the garage, put my gear on, and, in the 95 degree heat, kicked it to life.
Well, not quite.
To my horror I discovered that I could kick through all 4 cycles without using the decompression valve. The last time I'd ridden was about three weeks previous. I'd ridden a long way in pretty high temperatures. I didn't *want* to have missed so much riding time, but my family situation had demanded it. We all know how that goes sometimes. I wasn't thinking about how long it had been since I'd ridden though, I was thinking about what damage the long ride in the heat might have done to a valve or the rings.
My woman was anxious.
I kicked and kicked and kicked -- checked the decompression valve to see if it was stuck open -- then kicked some more.
"Look, I need to get going babe ..."
She had that semi-annoyed, quizzical look on her face of somebody who has a schedule to keep and you're the one keeping them from adhering to it.
"I don't understand", I muttered. "It was fine last time I rode it."
Kick. Kick kick kick.
Finally it thumped once or twice and died.
Sweating, I kicked some more, and when that failed put my head down on the forks. I couldn't take my Jeep, because it was misfiring -- and now I couldn't take my Bullet because it wouldn't fire at all.
In frustration I admitted defeat.
"Sorry babe. I just don't know what's wrong. Guess it's not my day to be riding. You'll have to go alone."
Then I kicked once more to punctuate the failure.
A-thump-thump-thump-thump-thump-thump-thump ...
I revved the motor gently, she kept going, my woman rolled her eyes.
"Finally!!!"
Off we went. Of course, we had to turn around and come back to the house after about half a mile because she forgot some paperwork she needed.
I grinned and figured that was my revenge, but on highway 183 she kept creeping way out in front of me. I pulled up next to her at a stoplight in Lockhart.
"Baby," says I, "I told you this bike only does 60 to 65 comfortably. You gotta slow down."
She bit my head off and said she'd never gotten above 55 and most of the time was at 50, and if she went any slower then she'd cause a wreck.
Ahead of us, down south toward Luling, I could see some rather ominous looking black clouds.
I told her I'd see her back at the house, and I figure she was glad to be rid of me.
On the way back I figured out using milage signs that my Bullet was going 60 MPH when the speedo was jumping around the 70 MPH mark. Heh. Optomistic Indian engineers! The other thing I pondered was why the bike hadn't wanted to start.
Thirty minutes later I was in my driveway testing the compression. It was solid -- no problems at all. I could no longer kick through all 4 cycles without actuating the decompression valve.
So, what was the problem?
The Bullet theoreticians over at the Yahoo Group Bulletech came up with what I figured was a reasonable explanation: when you let the Bullet sit for an extended period you can get a case where the oil lining the cylinder wall drains out to such an extent that there's not enough fluid to create a hydrostatic seal between the rings and the cylinder wall.
At first that seemed ... well, unlikely.
But several posts showed up describing the same symptoms I had and describing that getting the bike running again -- however briefly -- could solve the issue. One poster said he had actually taken out the plug and squirted a small amount of oil in the cylinder -- and it fired up first kick after that.
That convinced me: hydrostatic seal it was.
The only thing that still annoyed me was how fast ... er, slooowww ... my Bullet was going. Next move: putting on the 18 tooth sprocket I've got sitting in my parts bin. It may not help a lot, but I think it ought to get me going a little bit faster without the high rev screech and vibrations from hell -- and I've got a sprung seat.
Actually I like going slow. But it will be some time before I get or build a big twin, and so if I can up the speed just a little and do some mechanical work for pleasure it's a win/win situation.
