Is this cylinder head usable?
Post Reply    Forum -> Not-So-Modern
Author Message
Addicted
1986 T5, 1971 Sprint
Joined: 30 Oct 2014
Posts: 516
Location: Oak Brook, Illinois
Mon Feb 17, 2020 10:56 am quote
Iím in the middle of a 1974 Veloce motor rebuild. I put the cases back together today and installed the piston and cylinder. I noticed that the cylinder head looks modified, maybe the previous owner stripped out the threads for the plug, it sure doesnít look right. Is the head usable or should I replace it?
Also the edge of the new piston sits about 1.5 mm below the top of the cylinder when itís at TDC, Is that where it should be?

AA152409-3A29-40A2-A962-434736E0EDBE.jpeg
Is that a thread insert?

F69C5B2B-F688-464E-8EF8-6820425A632A.jpeg
New piston at TDC

Ossessionato
73 Rally, 74 Rally, 76 ET3, 80 P200, 06 PX150, 65 Li225 Silver Special, 86,95,96 Elite 80s, 2015 HD Road Glide Special, 2011 Ural Tourist
Joined: 18 Jan 2012
Posts: 3404
Location: Oceanside/ SF
Mon Feb 17, 2020 11:16 am quote
If the head doesnít leak and the squish gap is correct with it installed Iíd give it a try. If either one is off Iíd find a new replacement $50-100.

With the head installed and torqued, whatís your current squish gap?
Addicted
1986 T5, 1971 Sprint
Joined: 30 Oct 2014
Posts: 516
Location: Oak Brook, Illinois
Mon Feb 17, 2020 12:14 pm quote
I tried to measure the squish, itís somewhere between 2.5 and 3 mm. I think the head has been modified.
Iíll start looking for a new or mote gently used cylinder head.

369358FA-B10B-449C-B5B5-94765A2B944C.jpeg

0B4B0680-D918-4CDA-8921-42078D1D0D75.jpeg

E1D6C46B-7EBC-450E-819A-0012E43A4C85.jpeg

Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 215
Location: Rochester, Minnesota
Mon Feb 17, 2020 12:57 pm quote
What are you using for a base gasket?
What are you using for a base gasket thickness? A squish around 1mm is usually what is desirable.

When your piston is at bottom dead center where is the top in relation to the exhaust and intake ports bottom? I've been told the bottom of the exhaust port should be even or a little below the top of the piston.
Style Maven
74 50s x3 78 P200 84 Cosa 58 AllState 68 Sprint 80 50special '66(?) Super125 + projects
Joined: 22 Nov 2010
Posts: 7606
Location: seattle/athens
Mon Feb 17, 2020 12:57 pm quote
I might try to smooth it and save it if I had to, but don't really like that insert somebody roughly slammed in there.
I'll have a look too. I think maybe......
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 215
Location: Rochester, Minnesota
Mon Feb 17, 2020 1:08 pm quote
V oodoo wrote:
I might try to smooth it and save it if I had to, but don't really like that insert somebody roughly slammed in there.
I'll have a look too. I think maybe......
You could try drilling out what is there and putting in a new insert. I've put inserts in other equipment without issue.

http://www.timesert.com/html/sparkplug.html
Style Maven
74 50s x3 78 P200 84 Cosa 58 AllState 68 Sprint 80 50special '66(?) Super125 + projects
Joined: 22 Nov 2010
Posts: 7606
Location: seattle/athens
Mon Feb 17, 2020 1:54 pm quote
Agree, if you HAD to, just get rid of all those sharp projections that will start glowplugging at the wrong time.
Addicted
1986 T5, 1971 Sprint
Joined: 30 Oct 2014
Posts: 516
Location: Oak Brook, Illinois
Mon Feb 17, 2020 3:32 pm quote
Christopher_55934 wrote:
What are you using for a base gasket thickness? A squish around 1mm is usually what is desirable.

When your piston is at bottom dead center where is the top in relation to the exhaust and intake ports bottom? I've been told the bottom of the exhaust port should be even or a little below the top of the piston.
I used the foil type base gasket that came in the gasket set, itís not adding much height to the cylinder.
I checked the exhaust port with the piston at BDC and itís sitting just above the bottom of the port. About where you said it should be.
Scooter Mercado has a cylinder head that looks correct for the Veloce motor for $40 bucks. Iíll probably go that route unless I find something used for less!
Also, (and please correct me if Iím wrong) it looks like with these older motors that have a dome type cylinder head, there isnít really a squish band at all.

337A3412-7308-4A31-A45B-0B51F91570AA.jpeg

Ossessionato
Joined: 22 Oct 2011
Posts: 4255
Location: Tega Cay, SC
Mon Feb 17, 2020 5:45 pm quote
I have a sprint 2 port head if that will work, but it is scalloped out like yours. Yours for the asking.
Addicted
1986 T5, 1971 Sprint
Joined: 30 Oct 2014
Posts: 516
Location: Oak Brook, Illinois
Mon Feb 17, 2020 6:00 pm quote
Tierney wrote:
I have a sprint 2 port head if that will work, but it is scalloped out like yours. Yours for the asking.
Thanks Tierney, Iíll send you a message.
Ossessionato
Joined: 22 Oct 2011
Posts: 4255
Location: Tega Cay, SC
Mon Feb 17, 2020 8:32 pm quote
I sent you one as well. thx
Hooked
2007 Stella 150
Joined: 02 Nov 2019
Posts: 215
Location: Rochester, Minnesota
Tue Feb 18, 2020 3:53 am quote
V oodoo wrote:
Agree, if you HAD to, just get rid of all those sharp projections that will start glowplugging at the wrong time.
I agree if I were using an insert I would clean up with a flap wheel afterward to blend everything in. You wouldn't even know it was there. I've used these often on a piece equipment with a steel bolt in aluminum. The threads literally fell apart over time and the stud would come out, it was really a bad design. The joint couldn't handle the stress. Once inserts were out in with high strength picture the issue went away.
Veni, Vidi, Posti
a not so normal vbb2 '64, a weirdo vbx '86 and a not so normal pts100 '82
Joined: 15 Jun 2009
Posts: 5551
Location: Indo
Tue Feb 18, 2020 11:49 am quote
If u ask me its does usable

Its muh more better then mine


Good luck with the sprint project and cheer
Scooting the Ozarks is a scooter rally held in Eureka Springs, Arkansas offering riders scenic twisty rides, poker run, and more.   Vespa Wasp Pin Badges   AF1 Racing Vespa Austin
Post Reply    Forum -> Not-So-Modern
[ Time: 0.2951s ][ Queries: 28 (0.0447s) ][ Debug on ]