Hello,
Long time since I've been on this forum. Rode the bike in May, ran good. Tried riding again last week, lack of power. Here's what's been done so far.

1. New plugs, oil change. No change in performance. Old Plugs looked good, nothing abnormal.

2. Checked ignition timing, It's a California emissions bike so I could see timing mark but it wasn't exactly where it should be. ( Cali timing is slightly retarded, so I've read.)

3. Valve adjustment. Nothing out of whack. No change in performance.

4. Cleaned carbs. I've always drained them at the end of the season and found nothing out of the ordinary. Carb boots were intact, no tears. No change in performance.

5. Compression check. WOT and all plugs removed. Could not get above 60# in each cylinder. (New compression gauge from Harbor Freight?)

6. Checked CCT. Seems to operate smoothly.

7. Thought maybe Cam chain jumped a tooth because the intake cam mark wasn't right where it should be. Rotated it up a tooth. Bike smokes like a MF now. White smoke. Will have to undo that. No change in performance.

8. Pulled carbs again. When doing so , I found one of the damn rubber emissions hoses coming out of the #2 intake was broken. Could this 1/16" intake leak cause such a lack of performance.

9. This bike has only 35,000 miles on it. Has never been without oil or coolant. I find it hard to believe that a head gasket has ruptured somewhere. It seems to lost performance from one day to the next.

10. I am currently removing all emissions plumbing from carbs and engine.

Any thoughts? Thanks!

 

Well I'm chasing down a lot of the same stuff with a 90 but was wondering if you could help me out. Could you possibly take a pic of your carbs, more specifically the vacuum lines you mentioned? I have no idea if mine are correct, the only hoses I see besides the fuel fill line are 2 coming from between each set of carbs, and they only go out about 6 inches and quit, no plugs and wide open.

As for your issue I'm at a loss. My carb boots are horrible do I'm ordering new ones. Do you hear any air sucking or blowing from around the motor while it's running? You can also blow smoke around your motor and see if it's getting moved anywhere.

 

"5. Compression check. WOT and all plugs removed. Could not get above 60# in each cylinder. "

That's probably it right there. However with HF stuff I would go rent one from Autozone so you can be sure. While your at it, do a leak down test to see where you are leaking.
You should be 125 PSI minimum, around 150 max for stock compression, then up from there if you have raised compression. Mine comes in at 165 PSI with my 13:1 compression ratio.

By chance have you pulled plugs again and seen if a grey powder was on them? Powder is too lean and is the cylinder burning away.
Or were they slightly wet?
Wet can cause fuel wash and nuke your rings, loosing your compression. Smell the crankcase oil. If it smells like gas, your hosed.

"8. Pulled carbs again. When doing so , I found one of the damn rubber emissions hoses coming out of the #2 intake was broken. Could this 1/16" intake leak cause such a lack of performance."

Airleaks are the enemy, they can cause carb circuits to not flow correctly, the engine to run lean or rich depending on what the air leak effects, and just be a nightmare to trace down. Fix all your leaks. A can of starting fluid can be used to locate leaks. Start the bike and start spraying around suspected air leaks hoses and boots. If it suddenly revs up quickly, you found one.

I seriously doubt the head gasket died. They are pretty much indestructible on this motor. The hurricanes only real weakness is the carbs(well besides parts availability). An improperly tuned carb can ruin an engine if its too lean or too rich.

Projo198, download the service manual from the sticky in this forum, it has photos and schematics of the lines for both emission and no emission versions of the intake.

 

Squirt some oil in the cylinders and see what happens to compression. Check oil to be sure its not getting gas in it.

 

You have a standard emissions bike (non-California) from your description.
The two open 6" hoses between the carbs are the float bowl vent lines. They are supposed to be open.

 

Will do. I've downloaded and printed it but the quality isn't so good. I'll look at it on the computer tomorrow. Sorry for hijacking this thread.

 

1. Removed emissions plumbing. Bike starts right up and idles and runs good up to 5000 rpm then starts to bog. I think I fixed the air leak, but maybe bogs due to bad compression or I caused another problem when taking apart the carbs to clean them. Don't know yet.

2. I checked compression again. First dry and then with 25ml oil in each cylinder. Results as follows...
#1- 60 lbs. then 90 lbs.
#2- 70 lbs. then 90 lbs.
#3- 65 lbs. then 105 lbs.
#4- 67 lbs. then 110 lbs.

3. Checked all plugs. They all came out clean, perhaps slightly wet. I did not smell any gas in the oil. I stuck my nose in the oil fill hole and I've had the valve cover off for valve adjustment.

4. White smoke is coming out the exhaust. I don't know how long it takes for oil to be burnt out of the exhaust system especially 25- 30 ml in the piston plus whatever other amount that dripped into the pistons while adjusting the valves. Rode it for a couple of miles last night, smoked really bad but tapered off. Rode it again this afternoon, didn't smoke at first but then did when it warmed up a bit.

5. Coolant level is good.

6. I have not done a leakdown test. It seems to me that it would be either bad piston rings or bad valves/ valve seals or both. Is it possible to obtain all the parts to fix this?

7. Thanks for posting regarding the 2 tubes ( carb vents ) hanging down underneath the carbs. I initially plugged those up as well when removing emissions plumbing. Doh! Bike ran like crap! I would not have known why unless that question was there ( including response, of course)!

Thanks for the responses. I have a lot of mechanical experience but none with engine internals or transmission internals. This bike has a lot of sentimental value to me.

 

Compression is not good based on your measurements. Rings usually cause blue/black smoke.


You should do a leak down test because that will isolate it to upper end (this seems to be most likely).


White smoke usually means head gasket and coolant leaking into the combustion chamber(s).


You should look for water in the oil or coolant going back to the coolant bottle. Also head gasket will sometimes cause bubbles in the coolant bottle. It all depends on where the gasket leak is.


One confusing thing with a head gasket is the poor compression on all cylinders. Could be a combination of valves and a blown head gasket.


Some parts are available for these engines, but not easy to find and some are very expensive.

 

Compression increasing when you add oil is usually a sign of bad rings. If there is a valve issue the oil won't make much difference.

White smoke, as mentioned, is usually head gasket. I'd definitely do the leakdown.

If you do pull the top end apart be VERY careful with those rings. They are super thin and super easy to bend. Ask me how I know.

I recently went through a re-ring on my 89 (details to follow in a new thread soon). It isn't easy to find over-sized pistons for this bike to re-bore. I ended up just replacing the rings and doing a light ball hone to refresh the cylinder walls since my bike only has 13k miles on it. To find rings I called Carter Motorsports in Vancouver, BC, Canada. The local US Honda dealer told me that the rings were no longer in production and that no one could get them. I live a few minutes from the Canadian border and so gave Carter a call. They had them for me in two days, still produced and still available (although they aren't cheap). The job itself is not that hard although it helps to have two people when sliding the cylinder back into place (see bent ring comment above)

Bogging sounds also like a loss of fuel. Is your fuel filter clean (or new) and is your fuel pump putting out full pressure?

Air leaks, to emphasize previous comments, will cause a lot of running poorly issues. I am primarily a Harley mechanic and this is a problem with HD because they have rubber o-rings to seal the intake to the heads. The o-rings dry out and cause a leak which has no visible signs except that the bike runs like crap. Starter fluid can be used but I prefer WD40. It also revs up the motor when sucked in and is a bit less explosive.

 

Yeah, the oil upping your compression is no good. I echo the above statements, it's probably rings. The crappy thing is you can't order any parts until you get the head off and make sure you don't have bad cylinder scoring. Nothing worse than ordering stock bore size rings and needing to bore it over .10, .20, or more to get rid of the scoring.
I just rebuilt a neighbors Rebel 250 that had one cylinder at 60psi and the other at 110psi. The one at 60psi needed .50 over to clear up the scoring caused by WAAAAAAY too rich of a carb setup. The good news is after the rebuild and with both cylinders bored over .50 it came out to 122psi compression.

JE and Wiseco both will make pistons and ring sets for you. They used to produce overbore pistons for the Cane back in the 90's, so they already have the specs and tooling. I know Wiseco will reproduce anything they made in the past again. Expect to spend some serious coin though. Contact Us Email - Wiseco Piston Inc.

I found these 25 over, but unknown provenance. They claim "OEM quality"
Honda CBR600 CBR600F Hurricane 25 Over Piston Set 1987 1989 Set of 4 | eBay


You're about 9hrs drive from me unfortunately. If you were closer and could get it here I would help with the rebuild.
[wink}Or you could buy mine!{/wink]

On another note I found these guys selling a few decent parts still for the cane while looking for piston kits for you.
1988 Honda CBR600F - Hurricane Motorcycle Parts - Aftermarket & Performance | MotoSport

These guys are in the UK, but have some IMPOSSIBLE to find parts still.
Honda CBR 600 FJ 88 Parts at Wemoto - The UK's No.1 On-Line Motorcycle Parts Retailer
Same with these guys, but in Sweden.
Honda Cbr600f Hurricane 1988 (j) Usa parts list partsmanual partsfiche

Both will ship to the US, but expect to PAY a premium for international shipping and currency conversions.