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A couple of questions on my newly acquired GS750

  • Thread starter Thread starter origional-dz
  • Start date Start date
O

origional-dz

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Hello. Trying to find the year of my GS750. The engine serial number is GS750-38303 I used the search feature but am unable to find what I was looking for. The engine right now is in a small utility/dune buggy and is smoking very heavy blue under acceleration and a little at idle. For compression I have 75-80 across the board with the engine hot. I think thats low, but the engine still really runs good and rips. The guy I got it from said he was running 112+ octane in it and I am thinking that may have cooked the rings. I need to know the year so I can order some parts. Any help would be greatly appreciated.

Here is the video of it running:
 
I THINK (at least on my 1000) 100 is the low end of spec on compression. That combined with the blue smoke (oil burning), says re-build to me...
 
1977 model, i think
the compression when new would be around 180psi
120 is the lowest factory spec limit
100 serviceable limit

but you re right, they seem to be pulling like an elephant even with low compression
wait till you re-build it though !

be prepared for more than just new rings if you want to get it to top condition
 
High octane fuel will not cook rings, low oil might, or overheating. How is the engine cooled? Does it get enough airflow?
 
What cools the engine in that beasty? Poor thing is probably running 300+ F sump temperatures every time out.
 
As for the cooling, I mounted a 10" 1570cfm electric radiator fan right in front of the engine/heads so it will follow the natural air path while you are driving. I was looking to get a cylinder temp or oil temp gauge. I guess I will have to get a cart gauge but they can only do one cylinder and are pretty expensive. Does anybody know the exact year so I can, order some parts, or are most of the GS750 series interchangeable?
 
I ordered a service manual for it a few days ago. Once I get the numbers for the stock cylinder bore compared to what I have I can order some parts. What is a good place to get parts? I checked a couple sites and nobody seems to have oversized pistons and rings.
 
Wiseco will likely have oversized rings and what not. Also, you may check www.Z1enterprises.com May actually require a call to them, but they can just about get anything, and if they cant they can tell you where to get it, and they do NOTHING but vintage UJMs so they KNOW their stuff, unlike local bike shop kid who doesnt know anything if it wasnt made with at least 160bhp :)
 
I don't think that fan is going to do it, unless your using it in the winter. Think about how much airflow it gets at 60MPH in the bike.

Interesting vehicle, but I wonder will it be worth investing in a rebuild for it? Maybe you could find another engine and swap? If your going to remove it to repair, might be faster just to replace it.
 
origional-dz said:
Once I get the numbers for the stock cylinder bore compared to what I have I can order some parts.
Click to expand...

no need to wait for measurements, the pistons are stamped with a number telling you if they are standard or oversized
if you want to get new pistons (you may not need them though) you may want to re-bore and use 850 pistons
very easy conversion
a bit more grunt doesnt hurt :-D
 
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