What Am I Looking At Here?

Joined
Sep 5, 2013
Messages
97
Location
Northeast Illinois
Bike
1994 ST1100
STOC #
8977
I've been working on the '94 I recently bought, knowing that there was a coolant leak. I though I had found the culprit (the reservoir hose was cracked at the thermostat), and just finished replacing it along with other bits and pieces. So, after believing I had it all figured out, I put the bike back together short of the tupperware and refilled the radiator. Minutes later, I see drips below the left side of the bike.

After pulling everything back out and tracing the drips back to the source, I find a small collection of coolant on the engine, below the item seen in the attached pictures. I'll be taking that out soon to see what the actual cause and location of the leak is, because it seems to be from below that part.

Now the question: What is that part? As best I can tell from the parts diagrams at BikeBandit, it's the water cover. Is that correct?

Sorry for the tilted pics. They rotated upon upload. The first and third by 90 deg counterclockwise, and the second by 180 deg.
 

Attachments

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British Columbia
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2021 RE Meteor 350
I, for one, will be interested to see what others say this is, because I have never seen that on either the '95 I owned, or my current '96. Unless it is part of the PAIR system, which I have not had on either bike. Is this in the V of the engine?
 
Joined
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2021 RE Meteor 350
My guess now is that you have a leak from one of the two hose connections from each head to the thermostat housing. ST1100's were notorious for leaks from those hoses and tightening the clamps was usually all that was needed. If the hoses are original, it would be wise to replace them and the elbows they attach to.
 

CWDUSMC

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Oct 5, 2007
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137
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Pensacola, Florida
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01 ST-1100
STOC #
7272
Don't know about the part but the hoses and "water joints" on top of the "V" are definitely a source of leaks over time. I replaced the hoses, one of the water joints (due to corrosion) and the O-rings on both joints and the water cover on my 2001. The O-rings were completely flattened out and at first I didn't even realize they were there. If you have it that far apart (carbs pulled), do the job completely so you don't have to go back in again! Hardest part was the "water pipe" & "water cover" connections due to working space limitations.

Ride safe,
 

sirepair

Let's RIDE!
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Location
Chillicothe, Ohio
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2003 ST1100P
STOC #
7105
The pictured items are part of the PAIR air induction system (emissions stuff). No coolant in those lines (shouldn't be!)

Likely leaking from one or both of the coolant lines or elbows from head to t-stat housing. You will have to pull the carbs to replace them. Replace the cast elbows, o-rings and hoses along with the carb "isolators" (boots). About $100 in parts.

I just did this on my 1100 a couple weeks ago.
 
Joined
Sep 10, 2011
Messages
2,210
Location
West Michigan
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'98 ST1100
STOC #
8470
I had a similar leak and the source of the leak was the connection at the small tube that connects to the thermostat housing. The coolant leaked down and was dripping off the radiator hose on the left side.
 
OP
OP
Loki WRX YZF
Joined
Sep 5, 2013
Messages
97
Location
Northeast Illinois
Bike
1994 ST1100
STOC #
8977
Thanks everyone for the information. DaveS gave me the same response, that he believed it was part of the PAIR system. I had the pleasure of meeting him in person this evening in Indiana. Great guy!

I'll be pulling hoses and joints soon, it seems. I'll make the order, first. sirepair, do you happen to have the parts numbers handy to save me some time?
 

sirepair

Let's RIDE!
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2003 ST1100P
STOC #
7105
4 Isolator. 16211-MT3-000
1 HOSE L 19504-MT3-000
1 HOSE R 19506-MT3-000
2 JOINT, WATER 19523-MT3-000
2 O-RING 91331-PC9-003

I use Service Honda for parts. Hope this helps.
 

John OoSTerhuis

Life Is Good!
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May 10, 2005
Messages
5,217
Location
Bettendorf, Iowa
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1991 SSMST1100
STOC #
1058
This should help a bit, Loki: http://www.st-riders.net/index.php?topic=3523

I’d recommend also ordering the “TUBE, AIR SUCTION VALVE (C)” (8604-MT3-730) which is on the list in that AOW link. This hose is often welded to the nipple on the front of the air box, making removing the carbs a real PITA!!! BTDT Just cut it off and replace with a new one.

Tip: leave the throttle cables alone when you pop the carbs. Just lift the carbs off/up and swing them to the left and set them on a cushioning towel on the frame. Also BTDT, when I replaced my under-carb hoses, etc. the second time.

Here’s some pictures of mine that may be of interest: http://www.st-riders.net/coppermine/thumbnails.php?album=40

Regards, John
 
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John OoSTerhuis

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Bettendorf, Iowa
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1991 SSMST1100
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1058
PS You should have and use the shop manual if you’re going to take on jobs like this. I highly recommend the official Honda manual.

Yes, the parts in your pictures are the valves (air suction units containing an Air Injection Valve and two Reed Valves) of the Exhaust Emission Control System (Secondsry Air Supply System)... AKA “PAIR”

The system’s schematics, description/operation, testing, etc. are in the Honda Service Manual (pages 1-30, 1-33, 5-17 taking a quick look just now). The online part sites have a separate fiche (Air Suction Valves) for the valves: https://www.ronayers.com/oemparts/a/hon/506ca607f870023420a3fa78/air-suction-valve

HTH

John
 
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John OoSTerhuis

Life Is Good!
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May 10, 2005
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Bettendorf, Iowa
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1991 SSMST1100
STOC #
1058
Can anyone tell me the torque value for the water joint bolts?
If the Honda Service Manual doesn’t list a value or cover the part, use the standard torque values table in chapter 1 (page 1-15 in mine). It lists values for type and size of fastener, e.g. 6mm flange bolt (8mm head) - 9Nm/0.9kgm/7ftlb.

John
 
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Joined
Sep 10, 2011
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2,210
Location
West Michigan
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'98 ST1100
STOC #
8470
If the Honda Service Manual doesn’t list a value or cover the part, use the standard torque values table in chapter 1 (page 1-15 in mine). It lists values for type and size of fastener, e.g. 6mm flange bolt (8mm head) - 9Nm/0.9kgm/7ftlb.

John
And tighten those two bolts alternately in small increments, to be on the safe side.

EDIT : After you receive the two elbows, inspect them carefully for any casting flashing, especially around the bottom of the nipple. Remove any flashing with a fine file to ensure a good seal.
 
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