# Looowww compression on front cylinder



## BIGCOUNTRY750 (Jun 23, 2009)

Alright guys Im just looking for a little help here. 

The bike is a 05 brute 750 with 1100 miles on it. I have never drowned it but I do ride it like I stole it. This little problem started about month ago. The bike started smoking a little not bad but enough to notice. Well we rode saturday and about 3hrs into the ride I decide to check the oil. It was about half way up the stick. I screw it all the way in to check it. So I added some to get it right below the full line. Rode for another 5 hrs or so and went home.

Well yesterday got to start it to take it off the trailer and it wouldnt start. Well I check the oil and it is barely showing. So I pull the air lid and getting fuel but notice the front cylinder is not moving as much air as the rear. So I add a little oil to it and BAM it fires right up. Ok well problem solved for now WRONG!!!!!!!

I claean it up and go to start it again and same thing as last time. I add oil to the front and it starts right up.

So with that said I think I am going to pull the motor and rering and throw in some new chains and a set of weber 150i cams. 

What do you guys think would have caused it to go to crap all the sudden??????


----------



## 70Chevelle (Nov 11, 2009)

Does it misfire at all? Have you done a dry & wet compression test? Could be carbon on the valves. You could do a leak-down test to see if its the rings or the valves.


----------



## NMKawierider (Apr 11, 2009)

So you drop a little oil into the front carb and it starts....right? Obviously the compression has gone to s**t. Because the oil raises it enough to start means its probably not valves but check them anyway. I have seen this is vehicles with bad scared cylinder walls, broken rings and cracked pistons. 

A little story about mine. I was running a K&N and decided to go to synthetic oil. The first 100 miles on the oil it lost half a stick's worth. Refilled it and I tried it one more time. Same thing...all on the front cylinder (plug was black). Put coventional back in and at the same time I found that the front seal surface of my K&N to the frame had a 50 thousands gap in it, letting in all kinds of stuff....and being on the front side, you guessed it...right into the front cylinder scratching the walls. Talk about POed. Now I have a TwinAir and with the conventional oil, it doesn't get by and its back to no usage, but I am very sure if I put synthetic back in, it will. So....I won't 

Just food for thought. I hope its something simple....but...


----------



## brute78 (Jul 26, 2009)

Hey I got a really noobe question..when checking compression do you just turn bike over with compression gauge inserted into spark plug hole and record pressure? and what should the pressure be?..Also where can i get a compression gauge that will fit my brute, I have one for a car but it doesnt fit obv.:thinking:


----------



## 70Chevelle (Nov 11, 2009)

First of all, make sure your batt is fully charged, the engine is warm, and I always make sure to clean around the plug really good. Put comp. gauge in cyl. to be checked, hold throttle wide open, and crank until the comp. gauge stops rising. Repeat on remaining cylinder. Usable range on a Brute 750, according to the shop manual, is 36-66psi. 

As for a Comp. gauge...I have this http://www.sears.com/shc/s/p_10153_12605_00947089000P?keyword=Compression

But you can get them cheaper at part stores. Just make sure it has a 10mm adapter...I believe that's the plug size on a brute.


----------



## brute78 (Jul 26, 2009)

Awesome great info thanks!


----------



## BIGCOUNTRY750 (Jun 23, 2009)

I am goning to do a comperrsion and leak down test this weekend. I tried it again last night with the same results. Bike will not start until you add a little oil to the front carb. It starts up and runs and seems to idle fine!! 

Thanks for the info guys


----------



## phreebsd (Dec 16, 2004)

70Chevelle said:


> First of all, make sure your batt is fully charged, the engine is warm, and I always make sure to clean around the plug really good. Put comp. gauge in cyl. to be checked, hold throttle wide open, and crank until the comp. gauge stops rising. Repeat on remaining cylinder. Usable range on a Brute 750, according to the shop manual, is 36-66psi.
> 
> As for a Comp. gauge...I have this http://www.sears.com/shc/s/p_10153_12605_00947089000P?keyword=Compression
> 
> But you can get them cheaper at part stores. Just make sure it has a 10mm adapter...I believe that's the plug size on a brute.


that's correct. 10mm


----------



## brute78 (Jul 26, 2009)

Well I did compression test today and 70psi on front cylinder and about 65psi on rear..which according to manual is in specification..but the brute still running real bad smoking,sputtering,back firing like crazy...maybe timing?


----------



## drtj (May 3, 2009)

Both plug wires have good connection? Just a guess


----------



## 70Chevelle (Nov 11, 2009)

What color is the smoke?

Have you checked the crankcase vent? I've heard these brutes sometimes like to puke oil out the vent, which gets sucked right into the engine.


----------



## BIGCOUNTRY750 (Jun 23, 2009)

You asking me that or brute 78??


----------



## NMKawierider (Apr 11, 2009)

brute78 said:


> Well I did compression test today and 70psi on front cylinder and about 65psi on rear..which according to manual is in specification..but the brute still running real bad smoking,sputtering,back firing like crazy...maybe timing?


Well, so it isn't a compression problem. Hmm...when I had a split carb boot, mine had hell starting cold and ran like ...well you know.. because it sucked raw air in the split and not through the carb where it could get fuel. Mine split right where the clamp sits on the head side. Another guy here discovered his used oil when his filter was somewhat dirty because it added extra vacuum to the crankcase vent tube and actualy would use enough to go off the stick on one ride.


----------



## drtj (May 3, 2009)

Both


----------



## drtyTshrt (May 27, 2009)

yes what color is the smoke? Could be a stuck choke on the front side of the carb.


----------



## brute78 (Jul 26, 2009)

Well my problem is white smoke at first then some black but gets a litlle better after bike has been running..also mine is fuel injected..


----------



## drtyTshrt (May 27, 2009)

Oh yeah I see that about the FI now on yours.
I was looking at Bigcountry750 his is '05


----------



## 70Chevelle (Nov 11, 2009)

BIGCOUNTRY750 said:


> You asking me that or brute 78??


Yea now that ya mention it, my question was directed more towards brute 78, but you also.

I guess we are now trying to fix two different quads with two different problems in one thread now!


----------

