Hot front head

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chadu607
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Hot front head

#1

Post by chadu607 »

Can someone tell me some reasons my front head would be so much hotter than the rear one? Just after idling a few minutes from a cold startup.
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Re: Hot front head

#2

Post by Doc37W »

1. Has a manifold leak on front head. More air pulled in = leaner mix in front head = hotter head. Spray carb cleaner around manifold clamps while running, if idle speeds up, you've found the leak. 2. Rear spark plug is missfiring. Less burning mixture = cooler rear head than front. Check condition of plugs, gaps & wires, check timing. Repair. Doc
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Re: Hot front head

#3

Post by 58flh »

Run a finger under both clamps/if wet you have a intake leak!/Use Viton seals & bubbletest before starting motor.----Respectfully Richie
chadu607
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Re: Hot front head

#4

Post by chadu607 »

I did have an intake leak that i thought I fixed. A couple weeks ago I did feel wet around the front intake port. i'll have to check it again. thanks. still very difficult to start. When trying to adjust the low idle on my bednix i was able to turn the screw in all the way without much change in the engine speed. it went up just a little. today looks like a nice day to work on it.
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Re: Hot front head

#5

Post by 58flh »

Once you have no bubbles//You will notice it will be getting harder to start in about 2-3 weeks!/Bubble her again & tighten just until no bubbles.I probably bubble 4X a season--The first 3 will happen fast as everything is finding its place!/But 4X in 2yrs. is not bad.They ALL do it!/You will find a wet clamp more then your comfy with when fresh/But after a few Tests You can STOP it & 1-kick it is!----Respectfully---Richie--PS---Bendix w/ADJ. jet is very nice on a pan!---Good-Luck
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Re: Hot front head

#6

Post by Northman »

Play around with backing off the clamp scews slightly and tightening again. Just because you think it's of equal tightness and everything setteled in place don't mean its so or that you don't have a leak.. Some times all it takes is just a slight tweak and it seals up tighter than a frogs ass.

I've done this while everything is hot and had excellent results, it not a substitute for bubble testing by any means, but can help. If you have a carb support bracket...or not...that could cause some potential issue if tweaked or mis positioned etc.

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Re: Hot front head

#7

Post by Excalibur »

To rule out possible causes, how about a compression check? Perhaps do a cold test first, then follow up with a hot test.
Try swapping the spark plugs between cylinders and see if the problem moves to the front cylinder. At least you can eliminate the plug.
Are you running solid lifters, could the rear tappet clearances be tight? I'd expect tight clearance here to show up on a cold compression test.
Does your 60? run dual point timer? Could spark to the rear be weak?
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Re: Hot front head

#8

Post by chadu607 »

I started up the bike and let it idle a few minutes and tried the test with the brake cleaner. I engine bogged when i tested the front intake and didn't change on the rear one. I went over the intake and tried removing the carb support bracket. It seems to pull the carb up and out. I need to slot it and bend it into a better shape. I re-torqued the head bolts before doing this and found a few that were about 10-15 lbs light.

The idle seemed to improve but still not right. i tried the brake cleaner test again and now get engine bog in front and rear intake!.
anyway.. more work to do for another day.

As per compression and plugs, been there and tested ok. about 100lbs per cylinder.
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Re: Hot front head

#9

Post by Bigincher »

Northman wrote: Sat Oct 21, 2017 5:36 pm....... all it takes is just a slight tweak and it seals up tighter than a frogs ass.
So..... Just how tight is a frogs ass...??

WATER-TIGHT...!!
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Re: Hot front head

#10

Post by Northman »

Well.....the last time I bubble tested a frogs ass it passed with no bubbles and 15 lbs of air. Lol.

Chadu607 if you get to the point that you've done everything possible within reason and taken care of the bracket issue etc. your patience is spent, you've pulled alot of hair out of your head and just can't take it anymore and are thinking you want to sell the bike. Don't.... Proceed with a very very thin dressing of hylomar on your viton o rings (that I hope you use) snug up, adjust, test, and have a blast riding your bike. Some will poo poo this, but I don't care. It works and stays working. Again it's a light dressing of it.

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Re: Hot front head

#11

Post by chadu607 »

Thanks Northman
I was going to ask that since i spent most of yesterday re-setting the o-rings trying to squeeze out the leak. I know some have used tape, others rtv but none seems like a good option. I will look into your suggestion. I see that hylomar comes in different specs.. is there one i should look at in particular?
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Re: Hot front head

#12

Post by Northman »

Blue non setting high performance. Permatex makes it also...
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Re: Hot front head

#13

Post by chadu607 »

So before trying RTV sealant I made a bubble tester and it worked out quite well. found and sealed that front air leak and worked in my carb support bracket so that I didn't need to move anything after the clamps were tight. I put the pressure at about 15lbs and sprayed the clamps with soapy water and listened for any bubbles. Was very noticeable so I kept adjusting the clamp and moving the ring around until I got no more bubbles.

Here's where i'm at:
1. Timing is correct because I had a friend do it who is on this forum and very knowledgeable and a lot of experience building these old bikes. (I may be handing mine over to him to figure this all out eventually). He set it with the mark just on the right side of the timing window.
2. Carb settings (Bendiz/Zenith) 1.5 turns out on the low and 3.5 turns out on the high adjustment (These are the initial settings as per the Bendix carb instructions).
3. Lifters are hydraulic. I recently replaced the solid conversion and set them dry at 1.5 turns from bottom. This is a technique told to me by a well known builder in NJ as well as what I have found on forums. I had tried 4 turns from 0 lash before but was very noisy.
4. Compression is fine.. just about 100/cyl. When kicking it, sometime I am unable to kick past the compression (i'm about 200lbs") which is much better than with the solid conversion kit I had before... I have to put the pedal as high as i can and then load all my weight on it. (sometimes it skips a gear and leaves me on the floor holding my knee in agony :))

I spent the last hour trying to kick it over taking a break every 10 minutes or so. I get absolutely nothing.. and I do have a nice blue spark on both plugs that i cleaned up down to the shiny metal. If I spray a little starting fluid then it will fire out the carb or out the exhaust but won't start the engine.

Assuming the NJ Motor Vehicles gets me my paperwork this week i'm going to have to hand it off to one of the two people in my area who are willing to look at it. people online here and else ware have given me a lot to go on and have been a great help, but I can't get over a couple issues that have I have been working on all summer.. Difficult start and loud valve noise.

Image
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Re: Hot front head

#14

Post by Bigincher »

Check the timing again, sounds like you're 180 degrees out. Once the front intake valve closes, it's at least 1/2 revolution before the timing mark appears in the hole.
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Re: Hot front head

#15

Post by Northman »

Try this, put your timing Mark in the hole, in the center, don't back the motor up if you pass it keep going in the forward direction to take your gear lash out. Where is the line on your timer lobe? Take your front plug in the wire run it to where you can see the plug good, behind the rear cylinder and to the right side. Now retard your timer. Turn the ign. On, rotate the timer to full advance WITH your plug grounded so you can see it where does it spark? At full advance? Not at all? Before full advance? With your Mark in the center of the hole this will be slightly late timing but your bike will run decent this way. After you get it running you can adjust with a strobe....

This is a starting point.

And don't use rtv. hylomar is not the same thing.

Northman
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