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Post fracture 1835 build thread
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QRP
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PostPosted: Tue Aug 03, 2021 9:30 pm    Post subject: Re: Post fracture 1835 build thread Reply with quote

I would definitely check geometry on both sides.
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boxer74
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PostPosted: Wed Aug 04, 2021 7:44 pm    Post subject: Re: Post fracture 1835 build thread Reply with quote

QRP wrote:
I would definitely check geometry on both sides.


Checked angles on the other side using Brian's phone app approach:

Zero lift = 9.8 deg.
Half lift = 0.3 deg.
Full lift = 9.6 deg

I'll take it!
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PostPosted: Mon Aug 16, 2021 6:52 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

So, big problem...

Got the engine completed on the weekend. Ran nicely through the 20 min cam break-in, so I let it cool, changed the oil, checked valve clearances and installed in the car. Upon starting it up, noticed more valvetrain noise while adjusting the carb at idle. I should have shut it off at that point and investigated but thought it was just rough running due to the carb being out of tune (I'm still a rookie). It seemed to improve as I made carb adjustments. I then went for the first test run and 2min from my house after going up and down a hill to try and seat the rings, I heard a loud rattling noise and immediately shut the engine off and coasted to a stop. Got my wife to bring the towbar and brought it home.

The noise sounded to be coming from the passenger side. I opened the valve cover and the cylinder #2 exhaust valve spring fell out in my hand along with its retainer. Thankfully I recovered both keepers so they weren't ingested somehow by the engine. Unfortunately the valve was left free to get smacked by the piston. I'm sure that was the awful noise I heard.

This morning, I took out the spark plug for cylinder #2 and it has been damaged. I also found that the #1 exhaust valve spring was also broken but still held captive by the rocker arm and retainer. When I pulled off the rockers, I was able to remove the retainer, both keepers and broken spring by hand easily. The #1 spark plug came out fine with no sign of damage so I think that piston is fine.

Photos are below. I plan to use an inspection camera through the plug hole on #2 to assess the damage. At this point, I'm assuming I have to pull the engine and pull the head off and at the least probably replace #2 piston and cylinder (luckily I have another salvageable set of AA 90.5s that I can steal one from - hopefully the weight is close enough).

Now, how did this happen? These were used heads that appear to have recently been rebuilt and originally had stock springs installed, but HD single springs of unknown mileage and origin were provided with the sale. I installed the HD springs on the heads myself after lapping the valves into the seats. In hindsight, I should have used new heads but I was trying to avoid escalating costs and delays. I realize this was wrong, but I want to make sure I didn't overlook something else. With a CB 2239 cam, I find it hard to believe that the spring coils were binding. But I also find it odd that both exhaust springs broke. Could it really just be old worn springs?

What should I be looking into before or during a tear down? I had been pretty careful checking rocker geometry too. I'm pretty demoralized at the moment.

This really stinks...


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Brian_e
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PostPosted: Mon Aug 16, 2021 8:27 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

So you broke 2 valve springs in one shot? Shocked

Any idea how old they were, or what brand? Did they have ANY surface rust on them? I didn’t look back, but are you running 1.25’s or stock rockers?

Your combo shouldn’t be maxing anything out valve train wise.

I think you must have gotten a shit set of mystery springs. Take the rest of them off and throw them in a faraway lake. Scat single HD springs are good.

Brian
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PostPosted: Mon Aug 16, 2021 8:31 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Brian_e wrote:
So you broke 2 valve springs in one shot? Shocked

Any idea how old they were, or what brand? Did they have ANY surface rust on them? I didn’t look back, but are you running 1.25’s or stock rockers?

Your combo shouldn’t be maxing anything out valve train wise.

I think you must have gotten a shit set of mystery springs. Take the rest of them off and throw them in a faraway lake. Scat single HD springs are good.

Brian


No idea of age or brand unfortunately. No surface rust that I could see but to be honest, I didn't inspect them super carefully (oops!). I've got stock rockers.

I'll know more once I can get an inspection camera into the #2 spark plug hole, but I'm bracing for the worst. If it's just a matter of new heads and a #2 piston and cylinder, I can stomach that and chalk it up to inexperience but I hope the bottom end is fine and that I don't have to open up the case and start over again from scratch.
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PostPosted: Mon Aug 16, 2021 8:46 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Do the valves still slide in and out of the guide??

It seems like you caught it quick, so hopefully the piston only got a couple of tag marks. If that’s the case, buff off the high spots, replace the valves if they are bent, and put it back together with new good quality springs.

If you didn’t replace them already, replace the exhaust valves as well. Like valve springs, it’s ever a good idea to try and re-use mystery exhaust valves.

Brian
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PostPosted: Mon Aug 16, 2021 8:49 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Brian_e wrote:
Do the valves still slide in and out of the guide??

It seems like you caught it quick, so hopefully the piston only got a couple of tag marks. If that’s the case, buff off the high spots, replace the valves if they are bent, and put it back together with new good quality springs.

If you didn’t replace them already, replace the exhaust valves as well. Like valve springs, it’s ever a good idea to try and re-use mystery exhaust valves.

Brian


The gouge on the spark plug worries me. Makes me think the valve head actually broke off and was rattling around.
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PostPosted: Mon Aug 16, 2021 12:03 pm    Post subject: Re: Post fracture 1835 build thread Reply with quote

Brian_e wrote:
Do the valves still slide in and out of the guide??


I missed responding to this. One of the two affected valves slides just fine. The other is recessed in the guide so I can't grab the stem. I tried turning the engine over manually to get that piston to TDC and it won't move past a certain point. I'm guessing the valve is bent/broken and wedged into the head. This is also explained by the gouge in the spark plug. I'll run a camera into the plug hole later today, but I'm expecting to see some carnage.

How far should I dig? Given it only ran this way for mere seconds, would that be enough to bend the connecting rod and mess up the crank or any bearings or could the short block reasonably be trusted without a full tear down?
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PostPosted: Mon Aug 16, 2021 6:44 pm    Post subject: Re: Post fracture 1835 build thread Reply with quote

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Ouch. Looks like there's no hole in the piston. The engine didn't lock up on me while driving. I heard the loud noise and shut it down immediately. I wonder if the valve head then fell down completely. It locks up the engine from rotating now obviously when I turn it over by hand.

Obviously will pull head and investigate further but I'm fearing the worst... Is my bottom end doomed?
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PostPosted: Mon Aug 16, 2021 7:30 pm    Post subject: Re: Post fracture 1835 build thread Reply with quote

Oh damn..

If there are no holes in the piston you might have lucked out. I would certainly pull the piston and carefully check the inside of the crown for any cracks, and maybe sand the top on a flat with some fine sand paper to see if the crown is dented in at all.
I would also pull the connecting rod and make sure it’s still straight and the wrist pin isn’t bent.

Good luck.

Brian
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PostPosted: Tue Aug 17, 2021 4:58 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Brian_e wrote:
Oh damn..

If there are no holes in the piston you might have lucked out. I would certainly pull the piston and carefully check the inside of the crown for any cracks, and maybe sand the top on a flat with some fine sand paper to see if the crown is dented in at all.
I would also pull the connecting rod and make sure it’s still straight and the wrist pin isn’t bent.

Good luck.

Brian


Can a bend in the rod be seen by eye or do I need to take it to a machine shop for inspection?

If I replace the piston and cylinder, does the piston need to be inspected as you note above or is that to learn more about the condition of the rod?
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PostPosted: Tue Aug 17, 2021 5:43 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

I would be inspecting everything on that hole with the problem.

Connecting rod straightness is hard to check, and you should probably swing it by a engine machine shop.

Brian
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PostPosted: Tue Aug 17, 2021 10:07 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

There is a dirty way to check rod straightness.. keep the rods on the crank and line up the small ends of two adjacent rods. Now put a wrist pin through both rods at the same time.

If it doesn't go, you definitely have a bent rod. If it does slide through both without a hammer, it's probably ok, or at least close 'nuff.
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PostPosted: Tue Aug 17, 2021 9:00 pm    Post subject: Re: Post fracture 1835 build thread Reply with quote

Tore it open tonight and was shocked but pleasantly surprised at the same time. Piston is obviously toast. Rings and cylinder are fine. Rod and wrist pin seem fine too. Damage to head is not as bad as I was expecting and may be fixable but this might be my excuse to order some Steve Tim's super stock heads.


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PostPosted: Wed Aug 18, 2021 7:11 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Sorry to hear about the damage to your engine. You took way more care and planning than I did with my own 1835cc engine, and mine's not been apart since 1986.
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PostPosted: Wed Aug 18, 2021 7:35 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

My motor guy from my racing days has several of those hanging up in his shop from some rather "enthusiastic" riders

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PostPosted: Wed Aug 18, 2021 8:40 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Lesson learned, and now you have a nice paper weight for the desk.

That chunk missing next to the plug hole is pretty bad. If this was a third world country it would probably work, but you already know the heads need more work anyways.

I have done lots of 1776/1835 engines with a 2239 cam. I use AA500 heads and clean them up and do a really good valve job. I don’t change the flange shape at all, and hardly touch the CB offset manifolds. All the work is in the valve bowls and a little in the chambers. Pretty easy really.

The Tims heads would work really good, but I think you are on the boardline between needing the 37mm intake and not needing it. I know an 1835cc, my 35x32 heads, 8.5, 2239, and kads works awesome. I just finished one for a local gal who jumped in and drove it from S.Dakota to Oregon last week. With 91gas, she got 28-30mpg, and her old school dad still can’t believe the power. He grew up driving bugs through the ‘70’s.

Basically....if you want to save a little money and do things yourself.....build your own stock valve heads. I can give you a few pointers through PM’s if you want.

Brian
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PostPosted: Wed Aug 18, 2021 8:42 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Brian_e wrote:
Lesson learned, and now you have a nice paper weight for the desk.

That chunk missing next to the plug hole is pretty bad. If this was a third world country it would probably work, but you already know the heads need more work anyways.

I have done lots of 1776/1835 engines with a 2239 cam. I use AA500 heads and clean them up and do a really good valve job. I don’t change the flange shape at all, and hardly touch the CB offset manifolds. All the work is in the valve bowls and a little in the chambers. Pretty easy really.

The Tims heads would work really good, but I think you are on the boardline between needing the 37mm intake and not needing it. I know an 1835cc, my 35x32 heads, 8.5, 2239, and kads works awesome. I just finished one for a local gal who jumped in and drove it from S.Dakota to Oregon last week. With 91gas, she got 28-30mpg, and her old school dad still can’t believe the power. He grew up driving bugs through the ‘70’s.

Basically....if you want to save a little money and do things yourself.....build your own stock valve heads. I can give you a few pointers through PM’s if you want.

Brian


It seems like I read your mind.

I just put in an order for stock valve size AA 500's bored for 90.5 and 48cc from AA.
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PostPosted: Wed Aug 18, 2021 8:44 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

Cusser wrote:
You took way more care and planning...


Sadly the one item I did not take care on (trusting used questionable heads and valve springs) was the item that failed. Thankfully I caught it before it took out the entire engine.
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PostPosted: Wed Aug 18, 2021 9:20 am    Post subject: Re: Post fracture 1835 build thread Reply with quote

This is what happens if you keep trying to run it.
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It broke the whole top of the piston out, then the valve head wound up getting wedged between a rod and the roof of the case. It was all a waste. Same thing. Used exhaust valve.

Brian.
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