Author Topic: Jay's intake cam mod gone bad...now updated (Read 6172 times)

tomacGTi · « **on:** May 30, 2007, 11:13:01 AM »

I decided to do Jay's intake cam mod yesterday and got it buttoned up too late to take it out for a spin.

Idled up fine after the carbs were re-synched and valves adjusted, set up the manual adjust cam tensioner and things seemed fine. Started the bike up this morning and once again, things seemed fine so I went for a spin to see how things were going to be different or if I needed to rejet.

About 3 miles from home on a higher-rev shift, I started to hear a weird vibration that seemed to come out of the exhaust , almost like a v-tech like shriek. I didn't push it past that point fearing the worst but disaster struck. The #2 cylinder rocker broke and tumbled down into the cylinder head where the cam chain resides.

Before I buttoned everything up, I checked all the timing marks etc, obviously I did something wrong. I was able to limp it home obviously down on power and one cylinder at the least so now the questions are:

-Should I just start looking for a new cylinder head and assume the valves are all shot? The compression turning the starter while the plugs were out was certainly not as strong as it used to be.

I'm almost certain that this is an interferance motor although it didn't jump timing, the marks for the cams (which were always off a bit even following the manual) were slightly off of TDC using the old screwdriver down #1 plug hole trick.

-Should I try to replace the rocker on #2 and try again?

Help!

-Randy

PitterB4 · « **Reply #1 on:** May 30, 2007, 12:57:35 PM »

Damn, Randy. That sucks (I sure have a gift for the obvious, don't I?)! I'm of no real help but I hope you get her straightened out easily. I was hoping to get out with you some time soon (see my new sig!).

gsxr400 racer · « **Reply #2 on:** May 30, 2007, 01:07:14 PM »

dam that sucks i got a rocker you can have send me picks if you can of the timing both sides of the motor to my email. you adjusted the exhaust to the intake cam specs right? Ive ran it at the track that way and liked it with no problems. Let me know what you need and I'll help you out with my spares hate to see anyone mess up there stuff because something worked for me and not you, I tend to see things abit differently from being a mechanic/ racer for 13+years so try to send some pics to me.

tomacGTi · « **Reply #3 on:** May 30, 2007, 01:17:18 PM »

Yeah, the whole thing sucks as work is going to have me travelling for the next month all over the place. It's just going to have to sit for the time being until I have more than 15 minutes to look at it. I ordered a new rocker arm assembly from Bike Bandit this morning and I'm sure it'll arrive when I'm not home. Thanks Jay, I ordered it before I checked here.

Trust me Jay, I certainly am not doubting that it worked for you, I'm just hoping it's something stupid that I did. I didn't even take it up to redline but it was stronger everywhere with the same jetting. FWIW, it let go at around 12k, I'm happy it didn't do more damage than it did and I was able to limp the thing home. The pisser is, it was the intake rocker on #2 that let go, not even the exhaust side. All the valve adjustments were made to .005 (mid range on the intake side). If anything, you only need one feeler guage if you do the mod.

I'm actually hoping that if I drop the motor down, put in a new rocker that it will start up and run but I have my doubts though especially with the valves. I should have taken pictures but I just buttoned it back up without. Trust me, when I spun the thing around a couple of times, the cams had lined up fine.

Rob, figures you get a street bike now! I've got a fine 400cc paperweight though! Hopefully it'll be sorted out soon enough and we'll be out once again.

-Randy

Red01 · « **Reply #4 on:** May 30, 2007, 03:54:06 PM »

Zero clearance or not, if you break a rocker arm, the valve is gonna go to the closed position, and closed wouldn't be a problem, clearance-wise. (Unless something was able to somehow jam the valve open - pretty unlikely). One that was bent and holding a valve open could be a problem in zero clearance motor if it held the valve open far enough.

Having an exhaust valve stuck closed might cause some problems because mixture is coming in and has nowhere to go, but an intake stuck closed wouldn't cause that problem because the exhaust would be trying to let gasses out, but there wouldn't be anything to let out.

Thief400 · « **Reply #5 on:** May 30, 2007, 11:38:55 PM »

I would fish out the broken piece and install a new rocker and give it a try. Rockers do fail from time to time

tomacGTi · « **Reply #6 on:** May 31, 2007, 09:28:07 AM »

Rocker's fished out and am awaiting it's replacement. I'm not exactly releived to know that these things break per se but then again, alot is being asked of it to spin up to 14k's for 25000 miles. I just wish I knew why it let go in the first place.

Pretty much from what everyone has told me, I'm going to give it a try. I'm hoping the possible skip in timing didn't do in the valves and if that's the case, we'll see.

tomacGTi · « **Reply #7 on:** June 18, 2007, 04:54:54 PM »

I should have assumed the valves got intimate with the pistons....

I got the rockers that Jay and BikeBandit had sent and got started on installing them. When I pulled the cams out, the intake cam had flatspotted the 3 other cylinders with intact rocker arms. Guess the rocker broke for a reason, the motor definately skipped timing and some valves met Mr Piston.

It had also galled up the surface of the remaining rockers bad enough that I for sure wouldn't reuse them. That and the intake cam (not the one modified for exhaust use) is trashed. Looking down the intakes, you can see streaks of fresh oil going down the intake valve stems, for sure the guides and the seals are trashed as well.

Anyone know if you can do a cylinder head insitu or does the motor need to be dropped?

-Randy

Bartjan · « **Reply #8 on:** June 18, 2007, 05:04:06 PM »

sounds like it will work with another cilinder head, but to be sure the pistons are intact you should remove the cilinder head...

Banditmax · « **Reply #9 on:** June 18, 2007, 05:13:19 PM »

You may get away without dropping the motor but its alot easier to work on with it out of the frame.

gsxr400 racer · « **Reply #10 on:** June 18, 2007, 06:44:48 PM »

Quote from: "tomacGTi"

Anyone know if you can do a cylinder head insitu or does the motor need to be dropped?

-Randy

yes you can due to the b4 uses bolts instead of studs for the cylinder and head.

Thief400 · « **Reply #11 on:** June 18, 2007, 11:20:48 PM »

for that short of a distance driven and that kind of damage to the cams and followers I would start to look for an oiling problem. Assuming the motor was in good condition before the swap and utterly destroying itself in a few miles sounds like the cams were getting no oil

tomacGTi · « **Reply #12 on:** June 19, 2007, 10:19:49 AM »

There was plenty of oil in the galley and on everything Chris, the galling etc was due to impact. The rocker arm let go because of contact.

The journals and cam carriers were all perfect. I need to whip the head off and see if the pistons are screwed but can't do a total teardown because I don't have a garage. The bike lives outside under a cover.

Banditmax · « **Reply #13 on:** June 19, 2007, 01:58:17 PM »

Pull the engine out the frame. The bike can survive without the cover.then put the cover over the engine parts when your not working on them.

interfuse · « **Reply #14 on:** June 19, 2007, 02:05:38 PM »

Pull the motor and get a friend to help bring it into the kitchen.

Author Topic: Jay's intake cam mod gone bad...*now updated* (Read 6172 times)

Author Topic: Jay's intake cam mod gone bad...now updated (Read 6172 times)